Olmsted County, Minnesota: History
The Wisconsin Territory was established by the federal government effective July 3, 1836, and existed until its eastern portion was granted statehood (as Wisconsin) in 1848. Therefore, the federal government set up the Minnesota Territory effective March 3, 1849. The newly organized territorial legislature created nine counties across the territory in October of that year. One of those original counties, Wabasha, had portions partitioned off in 1853 to create Fillmore and Rice counties. Then on February 20, 1855, portions of Rice, Wabasha, and Fillmore counties were partitioned off to create the present county, with Rochester (which was also platted that year) as county seat. The county name recognized David Olmsted (1822–1861), a member of the first territorial council and the fourth mayor of St. Paul.
The county boundaries have remained unchanged since 1855.