Channel Islands National Park 's mainland visitor center received 342,000 visitors in 2014 . The islands attract around 70,000 tourists a year , most during the summer . Visitors can travel to the islands via public boat or airplane transportation . Camping grounds are available on Anacapa , Santa Rosa , Santa Cruz , San Miguel , and Santa Barbara Islands in the Channel Islands National Park . Attractions include whale watching , hikes , snorkeling , kayaking and camping . The United States Navy controls San Nicolas Island and San Clemente Island , and has installations elsewhere in the chain . During World War II all of southern California ’s Channel Islands were put under military control , including the civilian-populated Santa Catalina where tourism was halted and established residents needed permits to travel to and from the mainland . San Miguel Island was used as a bombing range and Santa Barbara Island as an early warning outpost under the presumed threat of a Japanese attack on California . San Clemente Island was used to train the Navy 's first amphibious force to prepare for Pacific combat against the Japanese in World War II . San Nicolas Island has been used since 1957 as a launch pad for research rockets . San Nicolas was considered ( out of eight possible locations ) as the site of the Trinity nuclear test . Santa Rosa Island was used in 1952 as a base for the USAF 669th AC&W Squadron and they operated two Distant Early Warning FPS-10 radars from the hilltops there . In 1955 another FPS-3 search radar was added , and in 1956 , a GPS-3 search radar was installed . A new MPS-14 long-range height-finder radar was installed in 1958 . The base was shut down in March 1963 , when the 669th was moved to Vandenberg AFB In Lompoc , California . The islands still house US Navy SEALs training facilities , including Naval Auxiliary Landing Field San Clemente Island
Trinity nuclear test
Trinity (nuclear test)
Channel Islands (California)