Lake Marshall Township is a township in Lyon County, Minnesota, United States. The population was 517 at the 2000 census. Lake Marshall Township was organized in 1872, and named for Lake Marshall. According to the United States Census Bureau, the township has a total area of 30.0 square miles, of which 29.6 square miles is land and 0.4 square mileā¦Lake Marshall Township is a township in Lyon County, Minnesota, United States. The population was 517 at the 2000 census. Lake Marshall Township was organized in 1872, and named for Lake Marshall. According to the United States Census Bureau, the township has a total area of 30.0 square miles, of which 29.6 square miles is land and 0.4 square miles is water.