Boundary Atlas

ZIP code 80503: Longmont, CO

ZIP code 80503 is in Longmont (71% of residents), Niwot (12%) and Gunbarrel (2.2%), in Boulder County (100%) and Larimer County (0.1%), Colorado. 15% of its residents live outside city limits. It is in Colorado's 2nd congressional district. Its state senate districts are State Senate District 17 (72%), State Senate District 18 (14%) and State Senate District 15 (14%); its state house districts are State House District 11 (73%), State House District 12 (18%) and State House District 49 (8.9%).

35,863residents (2020 Census)
91.7 sq miland area
4cities and towns
1congressional district
27voting precincts

See it on the mapAll of Colorado

City and county

City or townShare of ZIP residents
Longmont71%
Niwot12%
Gunbarrel2.2%
Lyons<0.1%

CountyShare of ZIP residents
Boulder County100%
Larimer County0.1%

Town or county subdivisionShare of ZIP residents
Longmont CCD96%
Boulder CCD4.3%
Berthoud CCD<0.1%
Loveland CCD<0.1%

Congressional district

Congressional districtShare of ZIP residents
Colorado's 2nd congressional district (CO-02)100%

Members of Congress

OfficeMemberContact
U.S. Representative (CO-02)Joe Neguse (D)202-225-2161
U.S. SenatorJohn W. Hickenlooper (D)202-224-5941 · contact form
U.S. SenatorMichael F. Bennet (D)202-224-5852 · contact form

Members serving now (119th Congress, until January 3, 2027). Source: Members of Congress: the @unitedstates project, congress-legislators (CC0).

State legislative districts

State senate districtShare of ZIP residents
State Senate District 1772%
State Senate District 1814%
State Senate District 1514%

State house districtShare of ZIP residents
State House District 1173%
State House District 1218%
State House District 498.9%
State House District 10land only

Voting precincts

27 voting precincts overlap ZIP 80503. Map them, with each precinct's share of the ZIP's residents.

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Your agent can get these cities, counties, districts and precincts with their shares, and their GeoJSON boundaries, from Boundary Atlas. Add https://atlas-production-d344.up.railway.app/mcp to Claude, ChatGPT, Cursor or Codex (free, no key; how), then:

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ZIP 80503 here is the Census Bureau's ZIP Code Tabulation Area, which approximates the USPS ZIP Code; PO-box-only ZIPs have none. Districts are the maps in force for the November 3, 2026 election.