Jefferson is an unincorporated town and a U.S. Post Office in Park County, Colorado, United States. It is located the northern end of South Park, along U.S. Route 285, approximately 15 miles (24 km) northeast of Fairplay, at the western foot of Kenosha Pass. It lies 6 miles (10 km) from Como, 23 miles (37 km) from Bailey, and 37 miles (60 km) from Breckenridge. The town consists largely of a strip of retail businesses along U.S. Route 285, as well as a small unpaved grid of houses and trailers on the south side of the highway. The most notable landmark in town is a historic one-room schoolhouse, highly visible in the surrounding grasslands of South Park. The Jefferson Post Office has the ZIP Code 80456.