They begin at the southeastern coast of the Florida peninsula, about 15 miles (24 km) south of Miami and extend in an arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry Tortugas.

Improved navigation led to fewer shipwrecks, and Key West went into a decline in the late nineteenth century.

The strongest hurricane to strike the U.S. made landfall near Islamorada in the Upper Keys on Labor Day, Monday, September 2, 1935.

Winds were estimated to have gusted to 200 mph (320 km/h), raising a storm surge more than 17.5 feet (5.3 m) above sea level that washed over the islands.

Hundreds of World War I veterans working on the roadway as part of a government relief program were housed in non-reinforced buildings in three construction camps in the Upper Keys.

Monroe County was unable to secure a $17 million loan through the state infrastructure bank, delaying work for at least a year.

While still open to pedestrians—walking, biking and jogging—if the bridge were closed altogether, only a ferry subsidized by FDOT and managed by the county would transport visitors to the island.

Today this highway allows travel through the tropical islands of the Florida Keys and the viewing of exotic plants and animals found nowhere else on the US mainland and the largest coral reef chain in the United States.

Key West traditionally had strong links with its neighbor ninety miles south by water, and large numbers of Cubans settled there.

The Keys still attract Cubans leaving their home country, and stories of "rafters" coming ashore are not uncommon.

[5][6][7] In 1982, the United States Border Patrol established a roadblock and inspection points on US Highway 1, stopping all northbound traffic returning to the mainland at Florida City, to search vehicles for illegal drugs and undocumented immigrants.

After one minute of secession, he (as "Prime Minister") surrendered to an officer of the Key West Naval Air Station (NAS) and requested US$1,000,000,000 in "foreign aid".

[8] The stunt succeeded in generating great publicity for the Keys' plight, and the inspection station roadblock was removed.

The northernmost island arising from the ancient reef formation is Elliott Key, in Biscayne National Park.

[10] The Florida Keys have taken their present form as the result of the drastic changes in sea level associated with recent glaciations or ice ages.

Several parallel lines of reef formed along the edge of the submerged Florida Platform, stretching south and then west from the present Miami area to what is now the Dry Tortugas.

The Upper Keys islands are composed of sandy-type accumulations of limestone grains produced by plants and marine organisms.

Rain falling through leaf debris becomes acidic and dissolves holes in the limestone, where soil accumulates and trees root.

The native flora of the Keys is diverse, including members of both temperate families, such as red maple (Acer rubrum), slash pine (Pinus elliottii var.

), growing at the southern end of their ranges, and tropical families, including mahogany (Swietenia mahagoni), gumbo limbo (Bursera simaruba), stoppers (Eugenia spp.

The Key Largo Woodrat is found only in the northern part of its namesake island and is a focus of management activities in Crocodile Lake National Wildlife Refuge.

The warm and sunny winter climate, with average highs around 75 °F (24 °C) and lows above 60 °F (16 °C), is the main tourist season in the Florida Keys.

Some of the more exposed vegetation in the keys is scrub, stunted due to the intense sun, quick draining sandy soil, and arid winter climate.

Hurricane Georges, after destroying much of the housing and infrastructure on many of the Caribbean islands, caused damage and extensive flooding in the Lower Keys in 1998, before making landfall in Mississippi.

In 2005, Hurricanes Katrina, Rita and Wilma affected the Keys (although none made a direct hit), causing widespread damage and flooding.

In response, many homes in the Keys are built on concrete stilts with the first floor being not legally habitable and enclosed by breakaway walls that are not strongly attached to the rest of the house.

Nonetheless, Monroe County, as reported in the Federal Register, has estimated that there are between 8,000 and 12,000 illegal enclosures inhabited by people.

[28] This influx of traffic, coupled with the two-lane nature of U.S. 1 through most of its length in the Keys, and the fact that no alternative road routes are available mean that Monroe County has the highest per capita rate of fatal automobile accidents in the state of Florida.

[29] The major industries are fishing and tourism, including ecotourism, with many visitors scuba diving in the area's protected waters.

A ferry takes riders between Key West and Fort Myers, as well as Marco Island due north on the mainland, along the western edge of Florida Bay.