So Minnesota: 2nd only to the Great Wall of China, Minnesota Correctional Facility-St. Cloud Wall

The Minnesota Correctional Facility-St. Cloud Wall is claimed to be the second longest continuous wall in the world, constructed between 1889 and 1916 by inmates using granite from the prison quarry. The 22-foot-high, 4.5-foot-thick wall spans over a mile and a half and is listed on the National Register of Historic Places.