Boundary Atlas

ZIP code 51101: Sioux City, IA

ZIP code 51101 is in Sioux City, in Woodbury County, Iowa. It is in Iowa's 4th congressional district. Its state senate districts are State Senate District 1 (100%) and State Senate District 7 (0.2%); its state house districts are State House District 2 (100%) and State House District 14 (0.2%).

1,146residents (2020 Census)
1.2 sq miland area
1cities and towns
1congressional district
3voting precincts

See it on the mapAll of Iowa

City and county

City or townShare of ZIP residents
Sioux City100%

CountyShare of ZIP residents
Woodbury County100%

Town or county subdivisionShare of ZIP residents
Sioux City city100%

Congressional district

Congressional districtShare of ZIP residents
Iowa's 4th congressional district (IA-04)100%

State legislative districts

State senate districtShare of ZIP residents
State Senate District 1100%
State Senate District 70.2%

State house districtShare of ZIP residents
State House District 2100%
State House District 140.2%

Voting precincts

3 voting precincts overlap ZIP 51101. Map them, with each precinct's share of the ZIP's residents.

Get this in your AI agent

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:

related_geographies(id="us:zcta:51101")

ZIP 51101 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.