When Europeans first arrived in the Florida Keys in the 16th century, the area was uninhabited or only sparsely inhabited by indigenous peoples such as the
Calusa and the
Tequesta. The earliest description of the area and its inhabitants was by
Hernando de Escalante Fontaneda, a survivor of a shipwreck who lived among the Calusa people from 1549 to 1566. The earliest reference to Key Largo is found on a map prepared in 1639 by Dutch cartographer
Johannes Vingboons, in which it is named
Caio des 12 Leguas (islet of twelve
leagues). Some time later, it was named
Cayo Largo — meaning long islet — by Spanish explorers. In 1770, Dutch surveyor
Bernard Romans reported that the area was uninhabited, although evidence was found that indigenous people visited the area from time to time. By the end of the
Third Seminole War in 1858, the area was under control by the United States government, though it remained largely uninhabited. In 1870, a post office was established at "Cayo Largo" (in the current Rock Harbor area). It closed and another was opened called "Largo" in 1881. Additional post offices opened in Planter in 1891 and Aiken in 1895. The island gained fame as the setting for the 1948 film
Key Largo, but apart from background filming used for establishing shots, the film was shot on a
Warner Bros. sound stage in Hollywood. After the film's success, pressure from local businesses resulted in a change in the name of the post office serving the northern part of the island, from "Rock Harbor" to "Key Largo", on June 1, 1952. After that, every resident north of
Tavernier had a Key Largo address and the postmark read "Key Largo". ==Geology and geography==