Whitman County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 47,973. The county seat is Colfax, and its largest city is Pullman.

Colfax is a city and the county seat of Whitman County, Washington, United States. The population was 2,782 at the 2020 census, making Colfax the second largest city in Whitman County behind Pullman. It is situated amidst wheat-covered hills in a valley at the confluence of the north and south forks of the Palouse River. U.S. Route 195, which forms the town's main street, intersects with State Route 26 at the north end of town; in the past, Colfax also lay at the junction of three major railway lines. It is part of the Pullman–Moscow combined statistical area. It was named after Schuyler Colfax, the vice president from 1869–73.