Deemed the 'King of the Missions,' Mission San Luis Rey de Francia was founded on June 13, 1798 and was the 18th Spanish mission established in California. Named after Saint Louis IX, King of France, the current church structure dates to 1811. By 1818, Mission San Luis was the most prosperous establishment in California, with six ranches under its charge, and by 1830, it became the largest building in California. The mission was designated as a National Historic Landmark under the U.S. National Register of Historic Places in 1970. The exterior of the church was stabilized and preserved in 1984, with various restoration projects continuing today. Currently in-progress is a system of modern earthquake retrofitting for the basilica.