Flensburg is a city in Morrison County, Minnesota, United States. The population was 216 at the 2020 census. After the Little Falls and Dak…Flensburg is a city in Morrison County, Minnesota, United States. The population was 216 at the 2020 census. After the Little Falls and Dakota Railroad was completed in 1882, there was a sidetrack to a mill at the site which later became Flensburg Village. The mill was called "Flen's Landing" or "Flynn's Siding", with a depot, and named for J. C. Flynn of Little Falls. Flynn was a teacher in the Little Falls schools in the late 1870s. Later, Flynn was an inspector for the Northern Pacific Railroad and a representative in the state legislature. He was also instrumental in developing the Little Falls & Dakota railroad which ran through the future town of Flensburg.