train251904 – Flagler decides to build the Over-Sea Railroad, but no official announcement is made.  During that time, surveyors and engineers work to provide Flagler with data and information. In May, the United States formally acquires the Panama Canal Zone. In July, the rail line to Homestead is completed.

1905 – Early in the year, preliminary surveys and mappings of channels and water over the Keys are completed. The FEC Railway begins construction of the extension from the mainland to Key West and completes the first rail section connecting Homestead to Jewfish Creek. State Bill 11 becomes law granting the FEC Railway rights to build the Key West Extension and granting the company a 200-foot right-of-way down the Keys.

1906 – The FEC Construction Division begins building a landfill for a railroad terminal in Key West that eventually covered 134 acres of land.

1907 – Central Supply in Islamorada is fully operational. Roadbed is finished on Stock Island.

1908 – A bridge to span the seven-mile stretch of water below Marathon is planned. On Jan. 22, the first regularly scheduled train from Miami to Knight’s Key (Marathon) arrives and the Over-Sea Railroad is a half-finished dream.

1910 – Workers drive the first spike at the Key West end of the Florida East Coast Railway on the Trumbo Island railhead.

1912 – A special Pullman sleeping car train leaves New York City Jan. 20, headed for Key West. On Jan. 21, FEC engineers place the final steel plate girder (span 36 of the Knight’s Key bridge) permanently in place. FEC engine 201 arrives in Key West at 2:45 a.m., the first engine and crew to cross the Bahia Honda Bridge and test tracks in the Lower Keys. The first FEC train arrives in Key West at 10:30 a.m. Jan. 22 with Flagler, now 82, and his wife Mary Lily Kenan in his luxurious office car with three bedrooms, a kitchen, salon and private bath. Following a Jan.  23 parade to commemorate the opening of the Over-Sea Railroad, a banquet is staged in the marine barracks where a message from President Taft is read and Flagler makes a brief speech.
Regular passenger service begins Jan. 22 with a 5 p.m. departure from Key West to the mainland.

The railroad operated from 1912 to 1935.

The 1935 Labor Day Hurricane washed away 40 miles of the Middle Keys section of the line. In addition, the Long Key Fishing Camp was destroyed, along with an FEC rescue train which was — with the exception of steam locomotive 447 — overturned by the storm surge at Islamorada, Florida.

With Flagler gone, the FEC was unwilling to repair a line that had never repaid its construction cost — an unknown figure at the time only hinted at by the federal valuation of $12 million ($203,417,476 today).It was later determined that the total cost of what had been derisively nicknamed “Flagler’s Folly” exceeded $50 million ($1,293,333,333 today), all from his personal fortune.