ZIP codes and county lines in Colorado

161 of the 530 ZIP code areas in Colorado, or 30.4%, 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: 530
In more than one county: 161
At least 5% in a second county: 127
Cross a state line: 7

How Colorado compares

Colorado ranks 27 of 52 (the 50 states, DC and Puerto Rico) by the share of its ZIP code areas that overlap more than one county. 62 of its counties have at least one split ZIP code area along an edge. 7 of its ZIP code areas also reach into Nebraska, New Mexico, Utah and Wyoming, so a ZIP list that is meant to stop at the state line does not.

Counties with the most split ZIP code areas

Arapahoe County: 25 ZIP codes shared with another county
Adams County: 24 ZIP codes shared with another county
Denver County: 22 ZIP codes shared with another county
Jefferson County: 19 ZIP codes shared with another county
Weld County: 17 ZIP codes shared with another county

Every split ZIP code area in Colorado

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
69168	Perkins County, NE 61.3% Chase County, NE 34.3% Sedgwick County 4.4%	38.7%	3
80002	Jefferson County 95.6% Adams County 4.4%	4.4%	2
80003	Jefferson County 86.0% Adams County 14.0%	14.0%	2
80010	Arapahoe County 51.0% Adams County 49.0%	49.0%	2
80011	Adams County 55.3% Arapahoe County 44.7%	44.7%	2
80012	Arapahoe County 99.6% Denver County 0.4%	0.4%	2
80014	Arapahoe County 90.1% Denver County 9.9%	9.9%	2
80016	Arapahoe County 95.4% Douglas County 4.6%	4.6%	2
80020	Broomfield County 59.7% Boulder County 25.1% Jefferson County 13.1% Adams County 2.2%	40.3%	4
80021	Jefferson County 66.5% Broomfield County 33.5%	33.5%	2
80023	Broomfield County 63.1% Adams County 36.9%	36.9%	2
80026	Boulder County 99.5% Broomfield County 0.5%	0.5%	2
80031	Adams County 89.9% Jefferson County 10.1%	10.1%	2
80102	Adams County 48.6% Arapahoe County 36.4% Elbert County 15.0%	51.4%	3
80103	Adams County 66.6% Arapahoe County 33.4%	33.4%	2
80105	Arapahoe County 59.2% Elbert County 28.1% Adams County 12.7%	40.8%	3
80106	Elbert County 79.8% El Paso County 16.6% Douglas County 3.6%	20.3%	3
80110	Arapahoe County 97.4% Denver County 2.6%	2.6%	2
80112	Arapahoe County 72.9% Douglas County 27.1%	27.1%	2
80120	Arapahoe County 98.9% Douglas County 1.1%	1.1%	2
80123	Jefferson County 49.6% Arapahoe County 31.4% Denver County 18.9%	50.4%	3
80125	Douglas County 99.8% Jefferson County 0.3%	0.3%	2
80128	Jefferson County 90.1% Arapahoe County 9.9%	9.9%	2
80129	Douglas County 99.5% Arapahoe County 0.5%	0.5%	2
80135	Douglas County 82.5% Jefferson County 17.5%	17.5%	2
80136	Adams County 68.6% Arapahoe County 31.4%	31.4%	2
80137	Arapahoe County 59.6% Adams County 40.4%	40.4%	2
80138	Douglas County 55.4% Elbert County 44.6%	44.6%	2
80212	Denver County 74.5% Jefferson County 18.6% Adams County 6.9%	25.5%	3
80214	Jefferson County 99.0% Denver County 1.0%	1.0%	2
80216	Denver County 72.1% Adams County 27.9%	27.9%	2
80220	Denver County 99.5% Adams County 0.3% Arapahoe County 0.2%	0.5%	3
80221	Adams County 88.5% Denver County 11.5%	11.5%	2
80222	Denver County 84.8% Arapahoe County 15.2%	15.2%	2
80224	Denver County 97.5% Arapahoe County 2.5%	2.5%	2
80226	Jefferson County 99.4% Denver County 0.6%	0.6%	2
80227	Jefferson County 85.6% Denver County 14.4%	14.4%	2
80230	Denver County 90.8% Arapahoe County 9.2%	9.2%	2
80231	Denver County 58.2% Arapahoe County 41.8%	41.8%	2
80232	Jefferson County 99.1% Denver County 0.9%	0.9%	2
80234	Adams County 97.8% Broomfield County 2.2%	2.2%	2
80235	Jefferson County 74.9% Denver County 25.1%	25.1%	2
80236	Denver County 96.4% Arapahoe County 3.6%	3.6%	2
80237	Denver County 99.8% Arapahoe County 0.2%	0.2%	2
80239	Denver County 79.9% Adams County 20.1%	20.1%	2
80246	Denver County 66.0% Arapahoe County 34.0%	34.0%	2
80247	Denver County 54.3% Arapahoe County 45.7%	45.7%	2
80403	Jefferson County 82.1% Gilpin County 12.5% Boulder County 5.5%	17.9%	3
80421	Park County 97.9% Jefferson County 2.1%	2.1%	2
80423	Eagle County 84.9% Grand County 15.1%	15.1%	2
80439	Clear Creek County 58.4% Jefferson County 41.6%	41.6%	2
80449	Park County 97.5% Chaffee County 2.5%	2.5%	2
80452	Clear Creek County 98.1% Gilpin County 1.9%	1.9%	2
80463	Routt County 75.8% Eagle County 24.2%	24.2%	2
80467	Routt County 93.5% Rio Blanco County 6.5%	6.5%	2
80470	Jefferson County 81.3% Park County 18.7%	18.7%	2
80498	Summit County 93.7% Grand County 6.3%	6.3%	2
80503	Boulder County 97.9% Larimer County 2.1%	2.1%	2
80504	Weld County 58.5% Boulder County 40.8% Larimer County 0.6%	41.5%	3
80513	Larimer County 64.2% Weld County 30.6% Boulder County 5.3%	35.8%	3
80516	Weld County 76.7% Boulder County 14.2% Broomfield County 9.2%	23.3%	3
80524	Larimer County 75.6% Weld County 24.4%	24.4%	2
80534	Weld County 80.5% Larimer County 19.5%	19.5%	2
80537	Larimer County 97.3% Weld County 2.7%	2.7%	2
80540	Boulder County 65.3% Larimer County 34.7%	34.7%	2
80549	Larimer County 94.8% Weld County 5.2%	5.2%	2
80550	Weld County 90.7% Larimer County 9.3%	9.3%	2
80601	Adams County 100.0% Weld County under 0.1%	under 0.1%	2
80603	Adams County 54.2% Weld County 45.8%	45.8%	2
80612	Weld County 84.8% Larimer County 15.2%	15.2%	2
80642	Weld County 70.6% Adams County 29.4%	29.4%	2
80643	Weld County 88.6% Adams County 11.4%	11.4%	2
80649	Weld County 63.9% Morgan County 36.1%	36.1%	2
80654	Morgan County 83.0% Adams County 9.1% Weld County 7.9%	17.1%	3
80701	Morgan County 74.1% Adams County 25.9%	25.9%	2
80723	Morgan County 83.4% Washington County 16.6%	16.6%	2
80731	Phillips County 59.9% Logan County 28.3% Yuma County 9.5% Sedgwick County 2.4%	40.1%	4
80733	Morgan County 60.2% Washington County 39.8%	39.8%	2
80734	Phillips County 77.0% Yuma County 23.0%	23.0%	2
80737	Sedgwick County 96.2% Deuel County, NE 3.8%	3.8%	2
80741	Logan County 77.9% Morgan County 14.6% Washington County 7.4%	22.1%	3
80742	Weld County 92.7% Morgan County 7.3%	7.3%	2
80759	Yuma County 92.1% Washington County 7.9%	7.9%	2
80807	Kit Carson County 94.5% Yuma County 5.5%	5.5%	2
80808	El Paso County 83.7% Elbert County 16.3%	16.3%	2
80812	Washington County 95.5% Yuma County 4.5%	4.5%	2
80815	Kit Carson County 73.2% Washington County 26.8%	26.8%	2
80816	Teller County 62.7% Park County 37.3%	37.3%	2
80817	El Paso County 76.5% Pueblo County 23.5%	23.5%	2
80818	Lincoln County 87.3% Washington County 12.7%	12.7%	2
80819	El Paso County 93.7% Teller County 6.3%	6.3%	2
80827	Park County 87.5% Teller County 12.5%	12.5%	2
80828	Lincoln County 53.4% Elbert County 46.6%	46.6%	2
80831	El Paso County 94.9% Elbert County 5.1%	5.1%	2
80832	Elbert County 80.9% El Paso County 14.4% Lincoln County 4.7%	19.1%	3
80833	Lincoln County 77.5% El Paso County 19.9% Elbert County 2.5%	22.5%	3
80835	Elbert County 94.3% El Paso County 5.7%	5.7%	2
80836	Kit Carson County 99.2% Yuma County 0.8%	0.8%	2
80861	Kit Carson County 99.2% Yuma County 0.8%	0.8%	2
80863	Teller County 71.3% El Paso County 28.7%	28.7%	2
80926	El Paso County 63.4% Fremont County 36.6%	36.6%	2
81008	Pueblo County 98.1% El Paso County 1.9%	1.9%	2
81021	Kiowa County 67.7% Lincoln County 32.3%	32.3%	2
81039	Pueblo County 57.1% Otero County 42.3% Crowley County 0.6%	42.9%	3
81041	Prowers County 96.3% Baca County 3.7%	3.7%	2
81045	Kiowa County 58.5% Cheyenne County 24.9% Lincoln County 16.6%	41.5%	3
81047	Prowers County 96.3% Kiowa County 3.6%	3.6%	2
81050	Otero County 96.7% Bent County 3.3%	3.3%	2
81052	Prowers County 75.8% Bent County 24.2%	24.2%	2
81054	Bent County 84.4% Las Animas County 8.1% Baca County 7.5%	15.6%	3
81055	Huerfano County 98.8% Costilla County 1.2%	1.2%	2
81058	Otero County 70.8% Crowley County 29.2%	29.2%	2
81059	Las Animas County 73.9% Otero County 26.1%	26.1%	2
81063	Crowley County 63.0% Lincoln County 37.0%	37.0%	2
81064	Baca County 80.6% Las Animas County 19.4%	19.4%	2
81069	Huerfano County 48.4% Pueblo County 36.2% Custer County 15.4%	51.6%	3
81084	Baca County 83.5% Prowers County 16.5%	16.5%	2
81089	Huerfano County 78.0% Las Animas County 22.0%	22.0%	2
81092	Bent County 79.2% Prowers County 19.3% Kiowa County 1.6%	20.8%	3
81101	Alamosa County 94.4% Conejos County 5.6%	5.6%	2
81120	Conejos County 92.1% Rio Arriba County, NM 7.9%	7.9%	2
81122	La Plata County 60.4% Archuleta County 39.6%	39.6%	2
81125	Saguache County 82.0% Rio Grande County 16.5% Alamosa County 1.5%	18.0%	3
81130	Mineral County 70.7% Hinsdale County 29.3%	29.3%	2
81132	Rio Grande County 51.4% Saguache County 48.6%	48.6%	2
81136	Alamosa County 80.3% Saguache County 19.7%	19.7%	2
81137	La Plata County 79.6% San Juan County, NM 17.3% Archuleta County 3.1%	20.4%	3
81144	Rio Grande County 91.6% Alamosa County 8.4%	8.4%	2
81147	Archuleta County 73.9% Hinsdale County 21.9% Mineral County 4.2%	26.1%	3
81151	Costilla County 56.8% Conejos County 43.2%	43.2%	2
81154	Rio Grande County 65.4% Mineral County 34.6%	34.6%	2
81201	Chaffee County 84.4% Fremont County 15.6%	15.6%	2
81220	Gunnison County 74.5% Montrose County 25.5%	25.5%	2
81226	Fremont County 88.4% Custer County 11.6%	11.6%	2
81230	Gunnison County 61.0% Saguache County 39.0%	39.0%	2
81248	Saguache County 65.8% Gunnison County 34.2%	34.2%	2
81253	Custer County 70.0% Fremont County 23.8% Pueblo County 6.2%	30.0%	3
81301	La Plata County 78.3% San Juan County 21.7%	21.7%	2
81323	Dolores County 52.2% Montezuma County 47.8%	47.8%	2
81324	Dolores County 52.9% San Juan County, UT 47.1%	47.1%	2
81325	Dolores County 51.1% San Miguel County 48.9%	48.9%	2
81328	Montezuma County 90.9% La Plata County 9.1%	9.1%	2
81403	Montrose County 66.8% Ouray County 33.2%	33.2%	2
81415	Montrose County 60.5% Delta County 39.5%	39.5%	2
81416	Delta County 56.7% Montrose County 43.3%	43.3%	2
81423	San Miguel County 90.0% Montrose County 10.0%	10.0%	2
81431	San Miguel County 65.1% Montrose County 34.9%	34.9%	2
81432	Ouray County 99.3% San Miguel County 0.7%	0.7%	2
81434	Gunnison County 91.8% Delta County 8.2%	8.2%	2
81621	Eagle County 64.9% Pitkin County 35.1%	35.1%	2
81623	Pitkin County 53.9% Gunnison County 24.0% Garfield County 16.5% Eagle County 5.6%	46.1%	4
81625	Moffat County 100.0% Routt County under 0.1%	under 0.1%	2
81630	Garfield County 76.6% Mesa County 23.4%	23.4%	2
81635	Garfield County 97.1% Mesa County 2.9%	2.9%	2
81637	Garfield County 53.9% Eagle County 46.1%	46.1%	2
81638	Moffat County 77.2% Routt County 22.8%	22.8%	2
81641	Rio Blanco County 83.0% Moffat County 16.9%	16.9%	2
81650	Rio Blanco County 60.0% Garfield County 40.0%	40.0%	2
81653	Routt County 87.5% Moffat County 12.5%	12.5%	2
82063	Larimer County 79.7% Albany County, WY 20.3%	20.3%	2
82082	Laramie County, WY 70.7% Banner County, NE 16.8% Kimball County, NE 10.7% Weld County 1.8%	29.3%	4

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

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