For several centuries wrecking was an important economic activity in the Florida Keys. During the 19th century wrecking in the Keys became a highly organized and regulated industry, with dozens of vessels and hundreds of men active in the trade at any given time. The Florida Keys form a long arc of islands extending from the southern end of the east coast of Florida to the Dry Tortugas. A line of shallow coral reefs, the Florida Reef, runs parallel to the Keys from east of Cape Florida to southwest of Key West, with dangerous shoals stretching west from Key West to the Dry Tortugas. This chain of reefs and shoals is approximately long, separated from the Keys by the narrow and relatively shallow Hawk Channel. The Gulf Stream passes close to the Florida Reef through the Straits of Florida, which is the major route for shipping between the eastern coast of the United States and ports in the Gulf of Mexico and the western Caribbean Sea. The combination of heavy shipping and a powerful current flowing close to dangerous reefs made the Florida Keys the site of a great many wrecks, especially during the 19th century. Ships were wrecking on the Florida Reef at the rate of almost once a week in the middle of the 19th century (the collector of customs in Key West reported a rate of 48 wrecks a year in 1848). For a period of almost 100 years, wrecking captains and wrecking vessels in the Keys had to hold a license issued by the Federal court. In 1858 there were 47 boats and ships licensed as wreckers.