The Soo Locks are one of less than 3,000 National Historic Landmarks in the entire country. It earned this special designation due to its contributions to the nation's industrial and commercial development since the 1850s and the architectural significance and integrity of many of its structures and buildings dating back to the late 19th Century. To maintain these historic elements while incorporating necessary technological and safety improvements, the U.S. Army Corps of Engineers works closely with the National Park Service and State Historic Preservation Office.