Its name - Spanish for "Big Mouth" - comes from the mouth of the waterway, called Boca Grande Pass, separating the southern tip of the island from Cayo Costa. The pass was used as a busy shipping point for many years, as the waters in the pass are naturally deep. Processed phosphate from the Bone Valley region was loaded onto waiting ocean-going cargo vessels via the Seaboard Air Line Railroad at the dock located on the southern tip of the island. Shipping business to the island declined in the late 1970s, as it was no longer cost effective to ship phosphate by rail to Boca Grande when it could be loaded at Tampa. The phosphate plant at Boca Grande was old and its tons-per-hour rate was slow. Therefore, it made economic sense to discontinue the operation. Evidence of the island's industrial past can still be seen.