The Cape Florida Light is a lighthouse on Cape Florida at the south end of Key Biscayne in Miami-Dade County, Florida. Constructed in 1825, it guided mariners off the Florida Reef, which starts near Key Biscayne and extends southward a few miles offshore of the Florida Keys. It was operated by staff, with interruptions, until 1878, when it was replaced by the Fowey Rocks lighthouse. The lighthouse was put back into use in 1978 by the U.S. Coast Guard to mark the Florida Channel, the deepest natural channel into Biscayne Bay. They decommissioned it in 1990.