Yerba Buena Island is a large, naturally formed island in San Francisco Bay, and was formerly known as Goat Island.
It's the not-quite-midway point of the San Francisco–Oakland Bay Bridge being the landing and transfer point for the Eastern Span and Western Span of the said bridge.
It is connected to Treasure Island, which is man-made, and like Treasure Island, much of YBI is in the process of being redeveloped, except for the portions occupied by the Bay Bridge and the Coast Guard.
Rock quarries on the island were an early source of stone for Oakland's harbor works. The quarry operator, Joseph Emery, later became the founder of Emeryville.