There are 2 US Post Offices in Custer County serving a total of 4,240 residents equating to 2,120 residents per post office. It's estimated that approximately 6,768 packages are handled across the 2 county post offices annually. Custer County is the tenth-least populous of the 64 counties in the U.S. state of Colorado. As of the 2010 census, the population was 4,255. The county seat is Westcliffe.