Jefferson City, officially the City of Jefferson and informally Jeff City, is the capital of the U.S. state of Missouri. It had a population of 43,079 at the 2010 census, ranking as the 15th most populous city in the state. It is also the county seat of Cole County and the principal city of the Jefferson City Metropolitan Statistical Area, the second-most-populous metropolitan area in Mid-Missouri and the fifth-largest in the state. Most of the city is in Cole County, with a small northern section extending into Callaway County. Jefferson City is named for Thomas Jefferson, the third President of the United States.