Key West is located 153 miles southwest of Miami and 90 miles north of Cuba making it the southernmost city in the continental United States. Key West lies at the western end of a 125 mile chain of keys or low islands which extends southwestward from the southeastern tip of mainland Florida. The Keys are linked by the Overseas Highway whose bridges and causeways straddle the numerous gaps in the chain. The average elevation of the Florida Keys is 5 feet above mean sea level. Key West is mostly 6 to 8 feet in the east, rising in the west to a plateau on the site of the old town of 12 to 18 feet.The status of the deep water facilities on the western shore of Key West has been affected by the decline in Navy usage of the port in the recent past, starting with excessing of the Naval Station at Fort Taylor (referred to locally as Truman Annex) in March 1974. This has produced a deterioration in the facilities offered by the port, though there has been some reversal of this trend and many of these limitations may gradually be rectified. Only the North Mole at Truman Annex is in regular use for berthing deep draft vessels including visiting Navy ships. The former submarine and repair piers inside the basin are used for berthing small craft, and in the early 1980s the quays and mole were littered with impounded craft from the 1980 Cuban refugee incident. The Naval Air Station, which has several annexes located in Key West itself, is the Navy's premier pilot training facility for transient tactical aviation squadrons. The Naval Air Station support the Navy's air units and is host to many tenant commands, including Joint Interagency Task Force East.