Quick answer
Alameda Island is the most populous island in the continental United States outside the New York City area, sitting in San Francisco Bay next to Oakland. It became an island in 1902 when a tidal canal was cut through the peninsula. The west end now holds the USS Hornet Museum, the carrier that recovered the Apollo 11 crew.
Full transcript
A Peninsula That Became an Island
This was a peninsula. In 1902 a canal was cut through the neck of the land to let tides scour the shipping channel on the Oakland side, and the strip became an island on purpose. A name chosen by popular vote in 1853 stuck: Alameda, Spanish for tree-lined avenue. On its south shore, in 1917, the Strehlow family opened a beach park called Neptune Beach — swimming pools, a carousel, a roller coaster, a Ferris wheel, and a nickname: the Coney Island of the West. In 1923 both the American snow cone and the popsicle were first sold here. The park closed in 1939, and the rides were auctioned off in 1940.
The Carrier at the End of the Island
The west end of the island is flat because the Navy filled the wetlands there in 1927 to build an airport, then expanded it into a naval air station that opened in 1940. In April 1942 the carrier Hornet loaded the bombers of the Doolittle Raid here before they sailed for Tokyo. The base closed in 1997. One carrier stayed behind: a different Hornet, the one that recovered the Apollo 11 crew in 1969 and opened as a museum in 1998. Today the hangar deck is a hall of planes and the flight deck shows you the whole bay.
What to Do
Stand on the flight deck of the Hornet and look across the water at the skyline you left. Then drive or bike to the south shore, to Crab Cove, where Neptune Beach used to stand; the bay now fills the space where the pools were. Two vanished places — a fun park and a working base — sit side by side on one small island. Walk the shore at Crown Memorial State Beach and try the modern version of that 1923 experiment: an ice pop, bought on the sand where the original was first sold.