Following the 1990 U.S. Census and associated realignment of Colorado congressional districts, the 4th Congressional district consisted of Baca, Bent, Cheyenne, Crowley, Elbert, Kiowa, Kit Carson, Larimer, Las Animas, Lincoln, Logan, Morgan, Otero, Phillips, Prowers, Sedgwick, Washington, Weld and Yuma counties, as well as portions of Adams, and Arapahoe counties.
Following the 2000 U.S. Census and associated realignment of Colorado congressional districts, the 4th Congressional district consisted of Baca, Bent, Cheyenne, Crowley, Kiowa, Kit Carson, Larimer, Lincoln, Logan, Morgan, Phillips, Prowers, Sedgwick, Washington, Weld and Yuma counties, as well as portions of Boulder, and Otero counties.