Abandoned Florida Keys Overseas Railroad Extension train transport Miami to Key West

The Overseas Railroad (also known as Florida Overseas Railroad, the Overseas Extension, and Flagler's Folly) was an extension of the Florida East Coast Railway to Key West, a city located 128 miles (206 km) beyond the end of the Florida peninsula. Work on the line started in 1905 and it operated from 1912 to 1935, when it was partially destroyed by the Labor Day Hurricane. Some of the remaining infrastructure was used for the Overseas Highway.

Henry Flagler (1830–1913) was a principal in Rockefeller, Andrews & Flagler and later a founder of Standard Oil during the Gilded Age in the United States. The wealthy Flagler took an interest in Florida while seeking a warmer climate for his ailing first wife in the late 1870s. Returning to Florida in 1881, he became the builder and developer of resort hotels and railroads along the east coast of Florida.

Flagler's rail network became known as the Florida East Coast Railway (FEC). By 1904, the FEC had reached Homestead, south of Miami.