Flanders' Block is a historic commercial building in Madelia, Minnesota, United States, built in 1872. From 1872 to 1878 it served as the county seat building of Watonwan County, housing the courthouse, offices, and jail. Flanders' Block was listed on the National Register of Historic Places in 1984 for having local significance in the theme of politics/government. It was nominated for its associations with the early development of Watonwan County's government.