Colfax (formerly, Alden Grove, Alder Grove, Illinoistown, and Upper Corral) is a city in Placer County, California, at the crossroads of Interstate 80 and State Route 174. It is part of the Sacramento–Arden-Arcade–Roseville Metropolitan Statistical Area. The population was 1,963 at the 2010 census. The town is named in honor of Vice President Schuyler Colfax (1869–73), a bronze statue of whom stands on Main Street near the railroad station. Some of the town’s notable features include the newly restored train depot (which houses the Colfax Museum and Chamber of Commerce), the downtown shops on Main Street, and Colfax High School, which serves a large surrounding area.

The 2010 United States Census reported that Colfax had a population of 1,963. The population density was 1,394.7 people per square mile (538.5/km²). The racial makeup of Colfax was 1,759 (89.6%) White, 4 (0.2%) African American, 26 (1.3%) Native American, 29 (1.5%) Asian, 2 (0.1%) Pacific Islander, 54 (2.8%) from other races, and 89 (4.5%) from two or more races. Hispanic or Latino of any race were 178 persons (9.1%).

The population was spread out with 499 people (25.4%) under the age of 18, 159 people (8.1%) aged 18 to 24, 501 people (25.5%) aged 25 to 44, 580 people (29.5%) aged 45 to 64, and 224 people (11.4%) who were 65 years of age or older. The median age was 37.9 years. For every 100 females there were 92.3 males. For every 100 females age 18 and over, there were 86.3 males.