Rancho Mirage is a resort city in Riverside County, California, United States. The population was 13,249 at the 2000 census, but the seasonal (part-time) population can exceed 20,000. In between Cathedral City and Palm Desert, it is one of the eight cities of the Coachella Valley. Rancho Mirage was incorporated in 1973 from a merger of Mirage Cove with five unincorporated areas known as the "Cove communities" (Desert, Magnesia, Palmas, Tamarisk and Thunderbird), but had 3,000 permanent residents at the time. Although the first modern settlements date back to the 1920s and 1930s, Rancho Mirage got its claim to fame after World War II. The Annenberg Estate or Sunnylands in the area, owned by philanthropist Walter Annenberg, had long been popular with the wealthy and powerful, including Frank Sinatra, Bob Hope, Fred Astaire, Ginger Rogers, Queen Elizabeth II, Mary Martin, Harry Caray and Lloyd Campbell and the Campbells. Several U.S. presidents have vacationed here, and Gerald Ford was a frequent visitor who later bought a house. The Betty Ford Center is located in the Eisenhower Medical Center of the town. President Gerald Ford was living in the town at the time of his death. Rancho Mirage boasts twelve golf courses, also known as country clubs. The city's first golf resort was the Thunderbird Guest Ranch, opened in 1946 for entertainers and business clientele. Other golf resorts are the Tamarisk, Mission Hills, the Springs, Sunrise, KSL Resorts' Rancho Las Palmas hotel (opened in 1979 to replace the Desert Air golf and private airport from 1954-1978), Rancho Mirage, Morningside, Mission Hills North Course, Westin Hotels Mission Hills resort, and Tuscania by Sunrise Company opened in 2006. The Agua Caliente Mission Band of Cahuilla Indians of Palm Springs runs the Agua Caliente Casino on the intersection of Bob Hope Drive and Ramon Road off Interstate 10, opened in 2002. The thriving casino is a popular destination for locals, tourists, and gambling enthusiasts. In 2008 the tribal board completed the expansion of the Agua Caliente resort, which includes a 12-story hotel and spa, as well as remodelling the casino and expanding the parking structures. A state-of-the-art theater for top name entertainers will open in the spring of 2009. Though the Agua Caliente Resort and Casino was just outside the border of Rancho Mirage in an unincorporated area, the City of Rancho Mirage included the property as part of the city in an agreement with the tribe so they would have access to police and firefighting services. Rancho Mirage has expanded its economy from one relegated to seasonal, resort-based and low-paying, to include more light industry and commerce by I-10 and the Union Pacific Railroad, high-end retail centers like the River shopping complex, opened in 2005 and built around an artificial lake that resembles a castle's moat.