The Four Level Interchange (officially the Bill Keene Memorial Interchange) was the first stack interchange in the world. Completed in 1949 and fully opened in 1953 at the northern edge of Downtown Los Angeles, California, United States, it connects U.S. Route 101 (Hollywood Freeway and Santa Ana Freeway) to State Route 110 (Harbor Freeway and Arroyo Seco Parkway).