Colorado's 1st congressional district

Colorado's 1st congressional district is a congressional district in the U.S. state of Colorado based primarily in the City and County of Denver in the central part of the state. The district includes almost all of the City and County of Denver and the Denver enclaves of Glendale and Holly Hills. A small portion of the City and County of Denver near Four Square Mile is located in Colorado's 6th congressional district.

The district has been represented by Democrat Diana DeGette since 1997. An urban and diverse district based in the heart of Metropolitan Denver and with a Cook Partisan Voting Index rating of D+29, it is the most Democratic district in both Colorado and the Mountain West. Only two Republicans have been elected to the seat since the Great Depression: Dean M. Gillespie was the district's representative from 1944 to 1947; and Mike McKevitt from 1971 to 1973, winning thanks to an ideological split among Denver Democrats. No Republican has even notched 30% of the vote in the district after 1998.

1990s
Following the 1990 United States census and consequential redrawing of Colorado's congressional districts, the 1st congressional district consisted of all of the City and County of Denver and parts of Adams, Arapahoe, and Jefferson counties.

2000s
Following the 2000 United States census and consequential redistricting of Colorado's congressional districts, the 1st congressional district consisted of all of the City and County of Denver and parts of Arapahoe County, including parts or all of the cities of Englewood, Cherry Hills Village, Sheridan, Aurora, and Glendale.

2010s
Following the 2010 United States census and consequential redistricting of Colorado's congressional districts, the 1st congressional district consisted of all of the City and County of Denver and parts of Arapahoe County including parts or all of the cities of Englewood, Cherry Hills Village, Sheridan, Aurora, and Glendale. The 1st district also took in additional area in the southwestern suburbs which included parts of Jefferson County and the CDPs of Columbine and Ken Caryl.

2020s
Following the 2020 United States census and consequential redistricting of Colorado's congressional districts, the 1st congressional district consisted of all of the City and County of Denver and parts of Arapahoe County that are enclaves within the Denver city borders such as Glendale and Holly Hills: the Jefferson County portions were moved to the 7th District, while the southern Arapahoe County suburbs were moved to the Aurora-based 6th District.

Cities of 10,000 people or more

 * Denver – 713,252

2,500 – 10,000 people

 * Glendale – 4,613
 * Holly Hills – 2,683