Jefferson National Expansion Memorial, St. Louis, Missouri, United States
Constructed between 1963 and 1965, the Jefferson National Memorial is a centerpiece for St. Louis. In addition to the iconic arch, the monument also includes an underground visitor center and museum. The World Monument’s Fund lists the site as endangered because there hasn’t been adequate funding to maintain the structure: “The preservation of twentieth-century materials and structural designs has proven challenging. The unusual shape and extreme height of the Arch compound these difficulties, as do economic trends that have led to decreased government funding for the stewardship of national monuments.”