Cole County is located in the central part of the U.S. state of Missouri. As of the 2020 census, its population was 77,279. Its county seat and largest city is Jefferson City, the state capital. The county was organized November 16, 1820, and named after pioneer William Temple Cole who built Cole's Fort in Boonville. Cole County is in the Jefferson City, MO Metropolitan Statistical Area. It is south of the Missouri River.