Stretching 111 miles into the open ocean, this engineering marvel connects the outlying islands of the Florida Keys to the mainland and forever changed more than just Florida

Traveling from Miami to Key West, Florida wasn’t always as carefree as it is today. In the early 20th century, the only way to reach the southernmost point of the continental United States was a day trip by boat, which depended on weather and tides.

But thanks to the stunning engineering marvel known as The Overseas Highway, which stretches 181 km miles from the southern tip of the continent through 44 tropical islands across 42 bridges, travelers seem to float along a necklace of mangroves and bays as they drive to the place, where North America and the Caribbean meet.

The Oversea Highway actually began construction as the Over-Sea Railroad and was the work of visionary Henry Morrison Flagler (known as the “Father of Modern Florida”).

In 1870, Flagler co-founded the Standard Oil Company with business magnate John D. Rockefeller, and it became one of the largest and most powerful corporations in the world at the beginning of the 20th century.

After visiting Florida and recognizing the tourist potential of the “Sunshine State”, Flagler poured much of his wealth into the region, building luxury resorts that turned one of the poorest states in the US into a winter paradise for tourists from the US Northeast from The Golden Age. However, guests have not been able to reach Flagler’s rich but remote resorts.

Thus, in 1885, Flagler connected a series of broken railroads along Florida’s Atlantic coast from Jacksonville, at the northern tip of Florida, to Miami, near the southern tip of the state. Miami was supposed to be the terminus of the line, but when the United States began construction of the Panama Canal in 1904, Flagler saw enormous potential for Key West, the closest American piece of land to the canal and the deepest port in the southeastern United States.

The bustling center was already thriving thanks to the production of cigars, mushrooms and fishing (by 1900 Key West was the largest city in Florida), but the island’s remote location made it difficult and expensive to transport goods north.

So Flagler decided to extend his route 150 miles (251 km) south to Key West, mostly over open sea. This so-called expansion was considered impossible by many of his contemporaries, and his vision was called “Flagler’s Folly” by his critics. Between 1905 and 1912, three hurricanes hit the construction site, killing more than 100 workers. Undeterred, Flagler pressed on.

The railroad took seven years, $50 million ($1.56 billion today) to build, and 4,000 African-American, Bahamian, and European immigrants who had to battle alligators, scorpions, and snakes while toiling in harsh conditions.

When the railway was finally completed in 1912, it was called the “eighth wonder of the world”. During the first launch of the Key West train from Miami, the then 82-year-old Flagler stepped out of his personal luxury carriage (which can be seen at the Flagler Museum in Palm Beach) and allegedly whispered to a friend, “Now I can die happy. My dream is fulfilled.”

The fact that Flagler funded more than $30 million out of his own pocket is remarkable,” says Florida historian Brad Bertelli. “Jeff Bezos or Bill Gates could do it today. Elon Musk with his SpaceX may be the best modern comparison.”

The railroad operated until 1935, when the deadliest hurricane in a century swept away miles of tracks. Instead of being restored, Flagler’s masterpiece was reshaped to accommodate America’s newfound love of cars.

In 1938, the US government set out to build one of the world’s longest causeways, relying on Flagler’s seemingly indestructible bridges that could withstand 200 mph winds. Crews laid the tracks so cars could run, and the newly opened Overseas Highway forever transformed the remote islands of the Florida Keys into the thriving tourist destination they are today.

More than a century after the railroad was completed, 20 of the original bridges still carry passengers from Miami to Key West. You can cover the distance in less than four hours, but getting around on the way is part of the fun. A series of fascinating, unusual stops help travelers better appreciate how this engineering marvel came to be and its lasting impact on the Florida Keys.

Key Largo is the northernmost part of the Florida Keys, 70 miles south of Miami, and is a great first stop. Alligators, snakes and other aquatic life may have terrified Flagler’s construction crews, but these days travelers come to Key Largo (the self-proclaimed “diving capital of the world”) to marvel at the abundant marine life. The Florida Keys National Marine Sanctuary, adjacent to John Pennekamp State Park, attracts scuba divers looking to dive into North America’s only living barrier reef.

The seagrass here is vital for fish, manatees and sea turtles, but the main attraction is swimming in the outstretched arms of Christ of the Deep, a submerged three-metre bronze statue of Jesus that has watched over visitors since 1965.

After this adventure, visitors head to Islamorada, a community located halfway between Miami and Key West that once housed a Marine Railroad station. Here at the Keys History and Discovery Center, a 35-minute documentary tells the story of the railroad’s construction and the many obstacles it encountered. The museum also displays artifacts from the train’s golden era, including dishes from the dining car, as well as an original menu where a steak cost $1.60.

  From 1908 to 1912, about 400 workers lived in a camp on Pigeon Key, a small coral island located 56 km south of Islamorada, while they built the most difficult part of the Oversea Railway – the famous Seven Mile Bridge (colloquially called ” The old seven”), which connects Middle and Lower Key.

In 1909, civil engineer William Jay Krum was tasked with the daunting task of crossing 10 kilometers of open water. Construction crews are working around the clock, driving more than 700 piers into the middle of the ocean, sometimes almost 9 meters below sea level, to build the world’s longest bridge. They are assisted by divers who help create underwater concrete footings to support the weight of the railway.

The remains of the old construction camp can be reached by taking a tourist train over the old bridge from the town of Marathon to Pigeon Key. A 3.5 km section (the only accessible section) reopened in January 2022 after a five-year, $44 million renovation. Closed to other vehicular traffic, the once crumbling bridge is now a safe playground for those who want to ride a bike or rollerblade 19 meters above the crystal clear water or watch marine life such as sea turtles and sharks.

Today, only four permanent residents live on Pigeon Key. The five-acre island is now a National Historic Landmark and is powered primarily by solar energy. It’s also home to a museum that offers guided tours of several buildings that once housed the workers and tells the story of what daily life was like for the crew who built the Seven Mile Bridge.

Travelers along the length of the Overseas Highway today know the trip is over when they see US Mile 1 in Key West.

The sign marks the southernmost point in the contiguous US, meaning travelers are now closer to Cuba (144 km south) than Miami (212 km north). But while many visitors head straight for the city’s main drag, Duval Street, or the Ernest Hemingway House and Museum, the small but informative From Sails to Rails Museum is worth checking out.