Mankato is a city in and the county seat of Jewell County, Kansas, United States. As of the 2020 census, the population of the city was 836. Ma…Mankato is a city in and the county seat of Jewell County, Kansas, United States. As of the 2020 census, the population of the city was 836. Mankato was originally called Jewell Center, and under the latter name laid out in 1872. It was renamed Mankato in 1880 after Mankato, Minnesota. Mankato was incorporated as a city in 1880.