ZIP codes and county lines in New York

332 of the 1826 ZIP code areas in New York, or 18.2%, overlap more than one county. If your territories, tax rules or service areas are set by county and your list is by ZIP, these are the rows where the two disagree.

ZIP code areas: 1,826
In more than one county: 332
At least 5% in a second county: 226
Cross a state line: 0

How New York compares

New York ranks 34 of 52 (the 50 states, DC and Puerto Rico) by the share of its ZIP code areas that overlap more than one county. 61 of its counties have at least one split ZIP code area along an edge.

Counties with the most split ZIP code areas

Oneida County: 22 ZIP codes shared with another county
Otsego County: 22 ZIP codes shared with another county
Delaware County: 21 ZIP codes shared with another county
Madison County: 19 ZIP codes shared with another county
Steuben County: 19 ZIP codes shared with another county

Every split ZIP code area in New York

Each row is one ZCTA and the counties its land falls in, largest share first. Counties in another state are marked with that state. Sort by the share outside the main county to put the most evenly divided ones first.

	Share of land by county
10463	Bronx County 95.8% New York County 4.3%	4.3%	2
10470	Bronx County 98.1% Westchester County 1.9%	1.9%	2
10509	Putnam County 99.9% Westchester County under 0.1%	under 0.1%	2
10512	Putnam County 99.9% Dutchess County under 0.1%	under 0.1%	2
10537	Putnam County 79.6% Westchester County 20.4%	20.4%	2
10541	Putnam County 96.0% Westchester County 4.0%	4.0%	2
10550	Westchester County 100.0% Bronx County under 0.1%	under 0.1%	2
10588	Westchester County 97.2% Putnam County 2.8%	2.8%	2
10803	Westchester County 99.2% Bronx County 0.8%	0.8%	2
10940	Orange County 96.0% Sullivan County 4.0%	4.0%	2
10963	Orange County 95.0% Sullivan County 5.0%	5.0%	2
10974	Rockland County 99.3% Orange County 0.7%	0.7%	2
11001	Nassau County 88.4% Queens County 11.6%	11.6%	2
11040	Nassau County 96.5% Queens County 3.5%	3.5%	2
11370	Queens County 58.0% Bronx County 42.0%	42.0%	2
11416	Queens County 99.6% Kings County 0.4%	0.4%	2
11417	Queens County 99.8% Kings County 0.2%	0.2%	2
11735	Suffolk County 54.0% Nassau County 46.0%	46.0%	2
11758	Nassau County 100.0% Suffolk County under 0.1%	under 0.1%	2
12009	Albany County 99.6% Schenectady County 0.4%	0.4%	2
12010	Montgomery County 63.7% Fulton County 18.6% Saratoga County 11.7% Schenectady County 6.0%	36.3%	4
12019	Saratoga County 97.8% Schenectady County 2.2%	2.2%	2
12023	Albany County 75.7% Schoharie County 24.3%	24.3%	2
12024	Columbia County 99.5% Rensselaer County 0.5%	0.5%	2
12025	Fulton County 63.9% Saratoga County 36.1%	36.1%	2
12027	Saratoga County 88.2% Schenectady County 11.8%	11.8%	2
12028	Washington County 52.8% Rensselaer County 47.2%	47.2%	2
12032	Hamilton County 57.8% Fulton County 42.2%	42.2%	2
12036	Schoharie County 78.2% Otsego County 21.8%	21.8%	2
12043	Schoharie County 97.2% Otsego County 2.8%	2.8%	2
12046	Albany County 96.3% Greene County 3.7%	3.7%	2
12053	Schenectady County 68.1% Albany County 16.9% Schoharie County 12.6% Montgomery County 2.3%	31.9%	4
12057	Washington County 81.7% Rensselaer County 18.3%	18.3%	2
12062	Rensselaer County 90.4% Columbia County 9.6%	9.6%	2
12064	Otsego County 62.1% Schoharie County 37.9%	37.9%	2
12066	Montgomery County 46.7% Schoharie County 30.4% Schenectady County 22.9%	53.3%	3
12068	Montgomery County 95.1% Fulton County 4.9%	4.9%	2
12070	Montgomery County 50.8% Fulton County 49.2%	49.2%	2
12083	Greene County 52.1% Albany County 47.9%	47.9%	2
12086	Saratoga County 57.2% Montgomery County 25.6% Fulton County 17.1%	42.8%	3
12087	Greene County 91.9% Albany County 8.1%	8.1%	2
12090	Rensselaer County 100.0% Washington County under 0.1%	under 0.1%	2
12093	Schoharie County 74.1% Delaware County 25.9%	25.9%	2
12094	Rensselaer County 85.2% Washington County 14.8%	14.8%	2
12095	Fulton County 91.6% Montgomery County 8.4%	8.4%	2
12118	Saratoga County 97.3% Rensselaer County 2.7%	2.7%	2
12120	Albany County 94.6% Greene County 5.4%	5.4%	2
12122	Schoharie County 91.5% Albany County 8.5%	8.5%	2
12123	Rensselaer County 98.1% Columbia County 1.9%	1.9%	2
12134	Hamilton County 65.3% Saratoga County 26.8% Fulton County 8.0%	34.8%	3
12137	Schenectady County 81.9% Montgomery County 18.1%	18.1%	2
12143	Albany County 88.5% Greene County 11.5%	11.5%	2
12149	Schoharie County 94.8% Otsego County 5.2%	5.2%	2
12154	Rensselaer County 55.1% Washington County 44.9%	44.9%	2
12155	Otsego County 92.8% Delaware County 7.2%	7.2%	2
12156	Rensselaer County 71.0% Columbia County 29.0%	29.0%	2
12157	Schoharie County 98.5% Schenectady County 0.8% Albany County 0.7%	1.5%	3
12160	Schoharie County 91.0% Montgomery County 9.0%	9.0%	2
12166	Montgomery County 97.8% Schoharie County 2.2%	2.2%	2
12167	Schoharie County 54.2% Delaware County 45.8%	45.8%	2
12184	Columbia County 98.3% Rensselaer County 1.6%	1.6%	2
12185	Rensselaer County 73.9% Washington County 26.1%	26.1%	2
12302	Schenectady County 91.0% Saratoga County 9.0%	9.0%	2
12303	Albany County 71.1% Schenectady County 28.9%	28.9%	2
12304	Schenectady County 66.3% Albany County 33.7%	33.7%	2
12306	Schenectady County 95.7% Albany County 4.3%	4.3%	2
12309	Schenectady County 81.5% Albany County 18.5%	18.5%	2
12406	Ulster County 69.2% Delaware County 30.8%	30.8%	2
12430	Greene County 58.6% Delaware County 41.4%	41.4%	2
12441	Delaware County 71.0% Ulster County 29.0%	29.0%	2
12455	Delaware County 94.6% Ulster County 5.4%	5.4%	2
12458	Ulster County 93.3% Sullivan County 6.7%	6.7%	2
12460	Albany County 64.6% Greene County 35.4%	35.4%	2
12463	Greene County 99.8% Ulster County 0.2%	0.2%	2
12465	Ulster County 77.5% Delaware County 22.5%	22.5%	2
12468	Greene County 84.4% Delaware County 15.6%	15.6%	2
12469	Albany County 59.7% Schoharie County 35.4% Greene County 4.9%	40.3%	3
12480	Greene County 52.5% Ulster County 47.5%	47.5%	2
12483	Sullivan County 76.1% Ulster County 23.9%	23.9%	2
12531	Dutchess County 83.6% Putnam County 16.4%	16.4%	2
12533	Dutchess County 92.4% Putnam County 7.6%	7.6%	2
12542	Ulster County 91.0% Orange County 9.0%	9.0%	2
12546	Dutchess County 78.9% Columbia County 21.1%	21.1%	2
12566	Ulster County 56.5% Orange County 33.5% Sullivan County 10.1%	43.5%	3
12567	Dutchess County 68.3% Columbia County 31.7%	31.7%	2
12571	Dutchess County 85.5% Columbia County 14.5%	14.5%	2
12582	Dutchess County 98.3% Putnam County 1.7%	1.7%	2
12583	Dutchess County 61.6% Columbia County 38.4%	38.4%	2
12589	Ulster County 84.7% Orange County 15.3%	15.3%	2
12721	Sullivan County 69.3% Orange County 30.7%	30.7%	2
12725	Ulster County 78.8% Sullivan County 21.3%	21.3%	2
12729	Orange County 53.9% Sullivan County 46.1%	46.1%	2
12740	Ulster County 63.5% Sullivan County 36.5%	36.5%	2
12758	Sullivan County 71.2% Ulster County 27.9% Delaware County 0.8%	28.8%	3
12760	Delaware County 78.5% Sullivan County 21.5%	21.5%	2
12763	Sullivan County 96.7% Ulster County 3.3%	3.3%	2
12776	Delaware County 61.3% Sullivan County 38.7%	38.7%	2
12780	Orange County 93.7% Sullivan County 6.3%	6.3%	2
12785	Sullivan County 78.1% Orange County 21.9%	21.9%	2
12789	Sullivan County 88.7% Ulster County 11.3%	11.3%	2
12804	Warren County 96.4% Washington County 3.6%	3.6%	2
12828	Washington County 74.4% Saratoga County 25.6%	25.6%	2
12835	Saratoga County 99.0% Warren County 1.0%	1.0%	2
12836	Warren County 97.5% Essex County 2.5%	2.5%	2
12839	Washington County 99.8% Warren County 0.3%	0.3%	2
12844	Washington County 89.6% Warren County 10.4%	10.4%	2
12847	Hamilton County 91.5% St. Lawrence County 8.5%	8.5%	2
12853	Warren County 99.0% Essex County 1.0%	1.0%	2
12857	Essex County 98.2% Warren County 1.8%	1.8%	2
12861	Washington County 99.0% Essex County 1.0%	1.0%	2
12870	Essex County 98.0% Warren County 2.0%	2.0%	2
12883	Essex County 98.8% Washington County 1.2%	1.2%	2
12911	Clinton County 80.6% Essex County 19.4%	19.4%	2
12912	Clinton County 76.3% Essex County 23.6%	23.6%	2
12913	Franklin County 55.6% Essex County 44.4%	44.4%	2
12914	Franklin County 84.0% St. Lawrence County 16.0%	16.0%	2
12920	Franklin County 92.7% Clinton County 7.3%	7.3%	2
12930	Franklin County 95.8% St. Lawrence County 4.2%	4.2%	2
12944	Essex County 87.8% Clinton County 12.2%	12.2%	2
12967	St. Lawrence County 97.7% Franklin County 2.3%	2.3%	2
12980	Franklin County 81.4% St. Lawrence County 18.6%	18.6%	2
12981	Clinton County 94.5% Franklin County 5.5%	5.5%	2
12983	Franklin County 51.4% Essex County 48.6%	48.6%	2
12986	Franklin County 75.2% St. Lawrence County 24.8%	24.8%	2
13021	Cayuga County 99.7% Onondaga County 0.3%	0.3%	2
13027	Onondaga County 99.3% Cayuga County 0.7%	0.7%	2
13030	Madison County 64.4% Onondaga County 35.6%	35.6%	2
13032	Madison County 99.7% Oneida County 0.3%	0.3%	2
13035	Madison County 96.8% Onondaga County 3.1%	3.1%	2
13037	Madison County 95.6% Onondaga County 4.4%	4.4%	2
13040	Cortland County 84.5% Chenango County 15.5%	15.5%	2
13042	Oneida County 63.6% Oswego County 36.4%	36.4%	2
13045	Cortland County 85.0% Cayuga County 8.8% Tompkins County 6.1%	14.9%	3
13052	Madison County 37.4% Chenango County 32.9% Cortland County 25.6% Onondaga County 4.2%	62.6%	4
13053	Tompkins County 57.7% Cortland County 42.3%	42.3%	2
13069	Oswego County 98.9% Onondaga County 1.1%	1.1%	2
13072	Madison County 77.5% Chenango County 22.5%	22.5%	2
13073	Tompkins County 97.6% Cayuga County 2.4%	2.4%	2
13074	Oswego County 94.6% Cayuga County 5.4%	5.4%	2
13077	Cortland County 83.9% Onondaga County 13.7% Cayuga County 2.4%	16.1%	3
13080	Onondaga County 62.7% Cayuga County 37.3%	37.3%	2
13082	Madison County 53.2% Onondaga County 46.8%	46.8%	2
13083	Oswego County 98.5% Jefferson County 1.5%	1.5%	2
13092	Cayuga County 90.8% Tompkins County 9.2%	9.2%	2
13104	Onondaga County 96.2% Madison County 3.8%	3.8%	2
13111	Cayuga County 82.4% Oswego County 17.6%	17.6%	2
13122	Madison County 81.7% Onondaga County 18.3%	18.3%	2
13126	Oswego County 99.1% Cayuga County 0.9%	0.9%	2
13135	Oswego County 73.8% Onondaga County 26.2%	26.2%	2
13136	Chenango County 99.9% Cortland County under 0.1%	under 0.1%	2
13141	Cortland County 64.8% Onondaga County 35.2%	35.2%	2
13143	Wayne County 55.3% Cayuga County 44.7%	44.7%	2
13146	Wayne County 96.4% Seneca County 3.6%	3.6%	2
13152	Onondaga County 85.8% Cayuga County 14.3%	14.3%	2
13156	Cayuga County 99.0% Wayne County 0.9% Oswego County under 0.1%	1.0%	3
13158	Cortland County 94.1% Onondaga County 5.9%	5.9%	2
13159	Onondaga County 68.0% Cortland County 32.0%	32.0%	2
13166	Cayuga County 98.2% Onondaga County 1.8%	1.8%	2
13304	Oneida County 89.6% Herkimer County 10.4%	10.4%	2
13309	Oneida County 73.5% Lewis County 26.5%	26.5%	2
13316	Oneida County 68.3% Lewis County 29.0% Oswego County 2.6%	31.7%	3
13317	Montgomery County 94.2% Otsego County 5.8%	5.8%	2
13320	Otsego County 100.0% Montgomery County under 0.1%	under 0.1%	2
13322	Herkimer County 60.0% Oneida County 40.0%	40.0%	2
13329	Fulton County 71.2% Herkimer County 28.9%	28.9%	2
13331	Herkimer County 98.7% Hamilton County 1.3%	1.3%	2
13332	Madison County 80.7% Chenango County 19.3%	19.3%	2
13338	Herkimer County 76.7% Oneida County 23.3%	23.3%	2
13339	Montgomery County 75.1% Herkimer County 18.6% Fulton County 6.3%	24.9%	3
13361	Herkimer County 76.9% Otsego County 23.1%	23.1%	2
13367	Lewis County 63.8% Herkimer County 36.2%	36.2%	2
13402	Madison County 93.0% Oneida County 7.0%	7.0%	2
13409	Madison County 94.2% Oneida County 5.8%	5.8%	2
13411	Otsego County 53.7% Chenango County 46.3%	46.3%	2
13413	Oneida County 88.8% Herkimer County 11.2%	11.2%	2
13421	Madison County 75.9% Oneida County 24.1%	24.1%	2
13425	Oneida County 86.0% Madison County 14.0%	14.0%	2
13431	Herkimer County 87.9% Oneida County 12.1%	12.1%	2
13437	Oswego County 75.5% Lewis County 24.5%	24.5%	2
13438	Oneida County 75.3% Herkimer County 24.7%	24.7%	2
13439	Otsego County 60.0% Herkimer County 40.0%	40.0%	2
13452	Fulton County 75.9% Montgomery County 24.1%	24.1%	2
13456	Oneida County 86.0% Herkimer County 14.1%	14.1%	2
13459	Schoharie County 89.6% Montgomery County 7.5% Otsego County 2.9%	10.4%	3
13460	Chenango County 96.0% Madison County 4.0%	4.0%	2
13464	Chenango County 98.3% Madison County 1.7%	1.7%	2
13470	Fulton County 70.1% Herkimer County 29.9%	29.9%	2
13471	Oneida County 81.4% Lewis County 18.6%	18.6%	2
13480	Oneida County 91.0% Madison County 9.0%	9.0%	2
13483	Oneida County 98.2% Oswego County 1.9%	1.9%	2
13485	Madison County 80.3% Otsego County 12.1% Chenango County 7.6%	19.7%	3
13491	Otsego County 51.8% Herkimer County 38.0% Madison County 10.1% Oneida County under 0.1%	48.2%	4
13493	Oswego County 99.5% Oneida County 0.5%	0.5%	2
13501	Oneida County 100.0% Herkimer County under 0.1%	under 0.1%	2
13502	Oneida County 70.3% Herkimer County 29.7%	29.7%	2
13601	Jefferson County 94.2% Lewis County 5.8%	5.8%	2
13608	Jefferson County 88.5% St. Lawrence County 11.5%	11.5%	2
13619	Jefferson County 54.3% Lewis County 45.7%	45.7%	2
13626	Lewis County 86.4% Jefferson County 13.6%	13.6%	2
13642	St. Lawrence County 91.8% Jefferson County 8.2%	8.2%	2
13646	St. Lawrence County 98.9% Jefferson County 1.1%	1.1%	2
13648	Lewis County 57.5% St. Lawrence County 42.5%	42.5%	2
13661	Jefferson County 96.4% Oswego County 3.6%	3.6%	2
13665	Lewis County 80.8% Jefferson County 19.2%	19.2%	2
13679	Jefferson County 74.8% St. Lawrence County 25.2%	25.2%	2
13682	Jefferson County 92.6% Lewis County 7.4%	7.4%	2
13691	Jefferson County 98.5% St. Lawrence County 1.5%	1.5%	2
13730	Chenango County 87.2% Broome County 12.8%	12.8%	2
13733	Chenango County 88.5% Delaware County 9.3% Otsego County 2.2%	11.5%	3
13736	Tioga County 75.4% Tompkins County 20.1% Broome County 4.4%	24.6%	3
13746	Broome County 60.5% Chenango County 39.5%	39.5%	2
13750	Delaware County 90.6% Otsego County 9.4%	9.4%	2
13754	Broome County 65.5% Delaware County 34.5%	34.5%	2
13760	Broome County 71.7% Tioga County 28.3%	28.3%	2
13775	Delaware County 98.3% Otsego County 1.7%	1.7%	2
13778	Chenango County 93.3% Broome County 6.7%	6.7%	2
13783	Delaware County 99.6% Broome County 0.4%	0.4%	2
13787	Broome County 66.6% Chenango County 33.4%	33.4%	2
13803	Cortland County 90.0% Broome County 10.0%	10.0%	2
13809	Otsego County 53.1% Chenango County 46.9%	46.9%	2
13811	Tioga County 91.0% Broome County 8.9%	8.9%	2
13813	Broome County 90.0% Chenango County 10.0%	10.0%	2
13820	Otsego County 70.4% Delaware County 29.6%	29.6%	2
13825	Otsego County 98.4% Delaware County 1.6%	1.6%	2
13835	Tioga County 59.1% Broome County 25.8% Cortland County 15.0%	40.9%	3
13838	Delaware County 96.3% Otsego County 3.7%	3.7%	2
13841	Chenango County 80.0% Cortland County 16.0% Broome County 4.1%	20.0%	3
13843	Otsego County 50.5% Chenango County 49.5%	49.5%	2
13849	Otsego County 54.0% Delaware County 46.0%	46.0%	2
13862	Broome County 98.7% Cortland County 1.3%	1.3%	2
13863	Cortland County 98.7% Broome County 1.3%	1.3%	2
13864	Tioga County 75.7% Tompkins County 24.3%	24.3%	2
14001	Erie County 78.6% Niagara County 13.0% Genesee County 8.3%	21.4%	3
14004	Erie County 82.4% Wyoming County 12.5% Genesee County 5.1%	17.6%	3
14009	Wyoming County 89.8% Cattaraugus County 10.3%	10.3%	2
14011	Wyoming County 89.9% Genesee County 10.1%	10.1%	2
14012	Niagara County 95.6% Orleans County 4.4%	4.4%	2
14013	Genesee County 97.9% Erie County 2.1%	2.1%	2
14024	Wyoming County 95.0% Allegany County 5.0%	5.0%	2
14030	Erie County 86.8% Cattaraugus County 9.8% Wyoming County 3.4%	13.2%	3
14037	Wyoming County 88.9% Erie County 11.1%	11.1%	2
14040	Genesee County 81.5% Wyoming County 18.5%	18.5%	2
14054	Genesee County 86.8% Wyoming County 13.2%	13.2%	2
14058	Genesee County 82.3% Orleans County 17.7%	17.7%	2
14060	Allegany County 55.2% Cattaraugus County 44.8%	44.8%	2
14062	Chautauqua County 99.7% Cattaraugus County 0.3%	0.3%	2
14065	Cattaraugus County 56.9% Allegany County 43.1%	43.1%	2
14070	Cattaraugus County 58.0% Erie County 42.0%	42.0%	2
14081	Erie County 77.1% Chautauqua County 20.6% Cattaraugus County 2.3%	22.9%	3
14098	Orleans County 98.1% Niagara County 1.9%	1.9%	2
14105	Niagara County 72.5% Orleans County 19.0% Genesee County 8.6%	27.5%	3
14125	Genesee County 98.6% Orleans County 1.4%	1.4%	2
14138	Cattaraugus County 63.8% Chautauqua County 36.2%	36.2%	2
14141	Erie County 83.0% Cattaraugus County 17.0%	17.0%	2
14145	Wyoming County 91.4% Erie County 8.6%	8.6%	2
14414	Livingston County 98.9% Monroe County 1.1%	1.1%	2
14416	Genesee County 87.2% Monroe County 12.8%	12.8%	2
14418	Yates County 89.4% Steuben County 10.6%	10.6%	2
14420	Monroe County 99.5% Orleans County 0.5%	0.5%	2
14422	Genesee County 94.3% Orleans County 5.7%	5.7%	2
14432	Ontario County 100.0% Wayne County under 0.1%	under 0.1%	2
14433	Wayne County 92.8% Seneca County 7.2%	7.2%	2
14437	Livingston County 83.8% Steuben County 16.0% Allegany County 0.2%	16.2%	3
14450	Monroe County 97.8% Wayne County 2.2%	2.2%	2
14456	Ontario County 77.0% Seneca County 21.9% Yates County 1.2%	23.0%	3
14464	Monroe County 95.5% Orleans County 4.5%	4.5%	2
14466	Ontario County 58.6% Livingston County 41.4%	41.4%	2
14470	Orleans County 96.4% Monroe County 3.6%	3.6%	2
14471	Ontario County 99.6% Livingston County 0.4%	0.4%	2
14472	Monroe County 81.5% Livingston County 15.6% Ontario County 3.0%	18.6%	3
14476	Orleans County 95.4% Monroe County 4.6%	4.6%	2
14482	Genesee County 90.8% Livingston County 7.5% Monroe County 1.7%	9.2%	3
14485	Livingston County 88.3% Ontario County 11.7%	11.7%	2
14487	Livingston County 76.8% Ontario County 23.2%	23.2%	2
14489	Wayne County 92.6% Ontario County 4.0% Seneca County 3.4%	7.4%	3
14502	Wayne County 96.2% Monroe County 3.8%	3.8%	2
14512	Ontario County 65.7% Yates County 27.3% Steuben County 5.5% Livingston County 1.5%	34.3%	4
14513	Wayne County 93.9% Ontario County 6.1%	6.1%	2
14519	Wayne County 97.5% Monroe County 2.5%	2.5%	2
14522	Wayne County 72.4% Ontario County 27.6%	27.6%	2
14525	Genesee County 56.9% Wyoming County 34.5% Livingston County 8.7%	43.1%	3
14530	Wyoming County 95.1% Livingston County 4.9%	4.9%	2
14532	Ontario County 87.5% Seneca County 12.5%	12.5%	2
14533	Livingston County 99.3% Wyoming County 0.7%	0.7%	2
14534	Monroe County 96.3% Ontario County 3.7%	3.7%	2
14536	Wyoming County 79.5% Allegany County 20.5%	20.5%	2
14544	Yates County 64.1% Ontario County 35.9%	35.9%	2
14546	Monroe County 96.6% Livingston County 3.4%	3.4%	2
14560	Ontario County 59.6% Livingston County 40.4%	40.4%	2
14561	Ontario County 98.5% Yates County 1.4%	1.4%	2
14564	Ontario County 96.2% Monroe County 3.8%	3.8%	2
14572	Steuben County 55.7% Livingston County 44.3%	44.3%	2
14580	Monroe County 99.2% Wayne County 0.8%	0.8%	2
14591	Wyoming County 95.7% Genesee County 4.3%	4.3%	2
14726	Cattaraugus County 88.3% Chautauqua County 11.7%	11.7%	2
14727	Allegany County 63.8% Cattaraugus County 36.2%	36.2%	2
14737	Cattaraugus County 99.0% Allegany County 1.0%	1.0%	2
14738	Chautauqua County 50.8% Cattaraugus County 49.2%	49.2%	2
14747	Chautauqua County 81.6% Cattaraugus County 18.4%	18.4%	2
14770	Allegany County 52.5% Cattaraugus County 47.5%	47.5%	2
14803	Allegany County 90.9% Steuben County 9.1%	9.1%	2
14804	Allegany County 99.9% Steuben County 0.1%	0.1%	2
14805	Schuyler County 95.1% Chemung County 4.9%	4.9%	2
14806	Allegany County 85.2% Steuben County 14.8%	14.8%	2
14807	Steuben County 54.8% Allegany County 45.2%	45.2%	2
14812	Schuyler County 57.2% Steuben County 24.4% Chemung County 18.4%	42.8%	3
14814	Chemung County 91.5% Steuben County 8.5%	8.5%	2
14815	Schuyler County 66.1% Steuben County 33.9%	33.9%	2
14817	Tompkins County 95.2% Tioga County 4.8%	4.8%	2
14822	Allegany County 87.4% Livingston County 12.6%	12.6%	2
14824	Schuyler County 66.7% Chemung County 33.3%	33.3%	2
14830	Steuben County 93.2% Chemung County 6.8%	6.8%	2
14836	Livingston County 59.0% Allegany County 41.0%	41.0%	2
14837	Yates County 68.2% Schuyler County 30.3% Steuben County 1.5%	31.8%	3
14838	Chemung County 93.8% Schuyler County 6.2%	6.2%	2
14840	Steuben County 99.5% Schuyler County 0.6%	0.6%	2
14841	Schuyler County 73.3% Seneca County 26.7%	26.7%	2
14843	Steuben County 96.3% Allegany County 3.7%	3.7%	2
14846	Livingston County 59.6% Allegany County 40.4%	40.4%	2
14847	Seneca County 97.0% Schuyler County 3.0%	3.0%	2
14859	Tioga County 59.4% Chemung County 40.6%	40.6%	2
14864	Chemung County 70.6% Schuyler County 29.4%	29.4%	2
14867	Tompkins County 97.7% Chemung County 2.4%	2.4%	2
14870	Steuben County 94.8% Schuyler County 5.2%	5.2%	2
14871	Chemung County 81.1% Steuben County 18.9%	18.9%	2
14877	Steuben County 99.9% Allegany County 0.1%	0.1%	2
14878	Schuyler County 75.2% Yates County 24.8%	24.8%	2
14883	Tioga County 69.9% Tompkins County 30.1%	30.1%	2
14886	Tompkins County 44.5% Schuyler County 42.5% Seneca County 13.0%	55.5%	3
14889	Chemung County 87.3% Schuyler County 8.7% Tioga County 4.1%	12.7%	3
14892	Tioga County 67.3% Chemung County 32.7%	32.7%	2
14897	Allegany County 92.0% Steuben County 8.0%	8.0%	2

What to do with this

If a ZIP code in your list is split, the ZIP alone cannot tell you which county an address is in. For most work that is fine. It matters when the county decides something: a sales tax rate, a licence, a franchise agreement written by county, or a service area somebody promised by county name.

The ZIP list audit checks your own list against the same Census data in your browser, and the ZIP spreadsheet comparison covers when a ZIP list is enough and when it is not.

What these numbers are, and are not

A ZCTA is not quite a ZIP code. ZIP Code Tabulation Areas are the Census Bureau's approximations of ZIP code areas, built by grouping census blocks by the ZIP codes of the addresses in them. USPS ZIP codes are delivery routes, not areas, and the two do not always match.
Some ZIP codes have no ZCTA at all. PO box ZIPs, ZIPs for a single building or a single large organisation, and military ZIPs usually have no area of their own, so they cannot be split across counties here and will not match any area in a map.
Land share is not population share. A ZCTA with 20% of its land in a second county might have almost none of its people there, or most of them. The shares here measure area, which is what the Census file publishes.
Tiny overlaps are included. A ZCTA counts as overlapping a county if the Census file lists any part of it there, including slivers along a road or river. That is why the share with at least 5% of land in a second county is shown alongside.

Source: U.S. Census Bureau, 2020 ZCTA to County relationship file, public domain. Counts use 2020 ZCTAs and 2020 county boundaries. ZIP codes added by USPS since then are not in it, and Connecticut's counties have since been replaced by planning regions in Census data.

Route by the boundary, not the ZIP

MapLogics decides who owns an address from a boundary you draw or import, so a ZIP that straddles two counties is answered by where the address actually is. There is a free trial if you want to see it on your own addresses.

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