Which US state capital city has the fewest residents?

Montpelier is the capital city of the US state of Vermont. It is the least populous state capital in the United States. The population was 7,855 at the 2010 census.

Pierre is the capital of the state of South Dakota. The population was 13,646 at the 2010 census, making it the second least-populous state capital after Montpelier.

Helena is the capital of the state of Montana. The population was 28,190 at the 2010 census, making it the fifth least-populous state capital after Augusta and Frankfort.

Jefferson City is the capital of the state of Missouri. The population was 41,297 at the 2010 census, making it the ninth least-populous state capital after Juneau, Dover and Annapolis.