I used to think the Overseas Highway was just another coastal drive until I actually drove it.
When Henry Flagler Decided to Build a Railroad Across Open Water in 1905
Here’s the thing about the Florida Keys—they weren’t supposed to be connected at all. Henry Flagler, this railroad tycoon who’d already built half of Florida’s east coast infrastructure, decided in 1905 that he’d extend his Florida East Coast Railway all the way to Key West, hopping across roughly 100 miles of open ocean and scattered limestone islands. People called it “Flagler’s Folly,” and honestly, looking at the engineering challenges involved—three hurricanes during construction, including the devastating 1935 Labor Day hurricane that killed over 400 people and destroyed much of the railway—maybe they had a point. But the man was obsessed with connecting Key West’s deep-water port to the mainland, convinced it would become the Gibraltar of America once the Panama Canal opened. The original railway, completed in 1912, used 546 concrete piers and cost around $50 million (something like $1.4 billion today, give or take). Flagler himself rode the first train into Key West at age 82, just a year before he died. Wait—maybe that’s why he pushed so hard.
The Seven Mile Bridge That Isn’t Actually Seven Miles Long
So the Seven Mile Bridge is actually 6.765 miles long, which I guess means someone rounded up for marketing purposes. It connects Knight’s Key in the Middle Keys to Little Duck Key, and it’s technically the longest bridge on the Overseas Highway, though there are 42 bridges total along the 113-mile route from mainland Florida to Key West. The current bridge opened in 1982, running parallel to the old railway bridge that Flagler’s engineers built—you can still see sections of the original structure, now used as a fishing pier and occasionally for film shoots (True Lies, 2 Fast 2 Furious, that sort of thing). What’s weirdly beautiful about driving it is the sensation of being suspended between two different shades of blue: the darker Atlantic on one side, the lighter Gulf of Mexico waters on the other. The engineering involved steel and concrete segmental construction, with the bridge rising 65 feet at its highest point to allow boat traffic underneath.
Island Hopping Through an Archipelago That’s Slowly Drowning
Anyway, the Keys themselves are ancient coral reef formations, built up over thousands of years when sea levels were higher, then exposed when the water receded. Key Largo, Islamorada, Marathon, Big Pine Key—each island has its own microclimate and ecosystem, though all of them sit at an average elevation of maybe 5-6 feet above current sea level. Which is, um, not great when you consider sea level rise projections. The mangrove ecosystems that line much of the highway are crucial nurseries for fish species and natural storm barriers, but they’re also migrating northward as temperatures warm. I’ve seen sections of the highway where you’re so close to the water that during king tides or storm surge, the road actually floods—Monroe County has documented over 50 tidal flooding events annually in recent years, and that number’s increasing.
Why Mile Marker Zero Feels Like Both an Ending and a Beginning
The Overseas Highway uses mile markers instead of traditional addresses, counting down from MM 126 near Florida City to MM 0 at Key West’s corner of Whitehead and Fleming Streets. Locals give directions exclusively by mile marker: “Meet me at MM 82” means you’re going to Islamorada’s Theater of the Sea. It’s disorienting at first, this countdown system, like you’re driving backward through space. But it also creates this weird psychological effect where you’re constantly aware of your progress, watching the numbers drop as the islands get smaller and the bridges get longer. By the time you reach Key West—the southernmost point in the continental U.S., just 90 miles from Cuba—you’ve crossed from the subtropical scrub of the upper keys through the pine rocklands of Big Pine Key to the Caribbean-influenced architecture and culture of Key West itself.
The Highway That Connects Islands But Also Isolates Them from What They Were
Turns out, connecting the Keys to mainland Florida changed them pretty fundamentally. Before the highway opened for automobile traffic in 1938, the islands were genuinely remote—accessible only by boat or Flagler’s railway. That isolation preserved both the ecosystem and the distinct Conch culture of Key West (“Conch” referring to people born in the Keys, though the term’s etymology is complicated). Now roughly 2.8 million tourists drive the Overseas Highway annually, bringing revenue but also traffic, development pressure, and environmental stress to ecosystems that evolved in isolation. The endangered Key deer population on Big Pine Key, for instance, faces constant vehicle strike mortality—around 100 deer are hit each year on a population that numbers maybe 800-1,000 total animals. Hurricane evacuation remains a major concern since there’s literally only one road out; when Hurricane Irma approached in 2017, the mandatory evacuation of all visitors and non-essential residents created a 30-hour traffic jam. I guess it makes sense that the thing connecting the islands is also the thing that makes them vulnerable, though I’m not sure Flagler would’ve seen it that way.
