Stewartville is a city in Olmsted County, Minnesota, United States. The population was 5,916 at the 2010 census, and was estimated to hav…Stewartville is a city in Olmsted County, Minnesota, United States. The population was 5,916 at the 2010 census, and was estimated to have grown to a population of 6,125 as of 2018. Stewartville has experienced growth as a result of its location just south of Rochester.