You’re driving south from Miami, the windows are down, and the air starts smelling like salt and coconut tan lotion. Suddenly, the land just... stops. You’re staring at a thin ribbon of asphalt stretching across an impossibly blue ocean. Most people heading down to Key West ask the same thing: how long is bridge to Florida Keys?
Well, it’s not just one bridge. It’s actually 42 of them.
If you’re looking for the big one—the monster that makes your knuckles turn white when a semi-truck passes you—you’re talking about the Seven Mile Bridge. But here is the kicker: it’s not actually seven miles long.
Honestly, the "Seven Mile Bridge" is a bit of a marketing lie. The modern bridge, completed in 1982, actually measures 6.79 miles (about 35,862 feet). The older, rickety railroad bridge it replaced was a tiny bit longer, but neither quite hits that perfect 7-mile mark. It’s close enough for government work, I guess.
The Overseas Highway: 113 Miles of Bridges and Islands
When you ask about the length of the bridge to the Florida Keys, you're usually thinking of the Overseas Highway (U.S. 1). This entire stretch runs about 113 miles from Key Largo all the way down to Mile Marker 0 in Key West.
It’s one of the most surreal drives in the world. You aren't just crossing water; you're basically skimming the surface of the Atlantic Ocean and the Gulf of Mexico.
Why are there so many bridges?
The Keys are an archipelago of about 1,700 islands, though the highway only connects the main ones. Back in the day, you had to take a ferry to get between them. It was a nightmare. Then Henry Flagler—a guy with more money than sense and a massive ego—decided to build a railroad through the ocean.
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- The Overseas Railroad (1912): Flagler’s "Eighth Wonder of the World."
- The 1935 Labor Day Hurricane: A Category 5 beast that literally blew the train off the tracks.
- The Highway Conversion (1938): The state bought the ruins and slapped pavement on top of the old railroad spans.
- The Modern Upgrade (1982): Most of the bridges we drive on today were built in the late 70s and early 80s to handle modern traffic.
The Seven Mile Bridge: The "Big One" Near Marathon
If you’re prone to vertigo, this is the part of the trip where you keep your eyes glued to the bumper in front of you. Located at the western end of Marathon, the Seven Mile Bridge connects Knight's Key to Little Duck Key.
It’s a box-girder structure. Basically, it’s made of 440 massive precast concrete sections.
One of the coolest things about it? The hump. Near the center, the bridge rises to a 65-foot clearance. This allows big boats to pass through the Moser Channel without the bridge needing a draw-span. If you’ve seen the movie True Lies (where Arnold Schwarzenegger jumps a limo off a bridge) or 2 Fast 2 Furious, you’ve seen this bridge.
The Ghost Bridge Next Door
As you drive the new bridge, you’ll see the "Old Seven" running parallel to you. It looks like a post-apocalyptic movie set. Sections are missing, and it just ends abruptly in some places.
That old bridge is a piece of history. For years, people used it for fishing and walking. A 2.2-mile section of it was actually restored recently (reopening in 2022) so people can walk or bike from Marathon out to Pigeon Key.
How Long Does the Drive Actually Take?
The distance from Miami to Key West is about 165 miles. On a map, that looks like a three-hour trip.
It’s not.
Don’t believe the GPS. Between the 45 mph speed limits through the small towns, the "one-way in, one-way out" traffic, and the sheer number of people stopping for Key Lime Pie, it’s usually a 4 to 5-hour trek. If there’s an accident on one of those narrow bridges? Forget it. You’re living there now.
Surprising Facts About the Keys Bridges
- Fresh Water: There’s a massive pipeline tucked inside the bridges that carries fresh water from the Florida mainland to the islands. Without it, Key West would be a very thirsty place.
- The Seven Mile Bridge Run: Every April, the bridge actually closes for a few hours so 1,500 runners can race across it.
- Shark Spotting: If you look down while driving (don't, but have your passenger do it), you can often see huge bull sharks and hammerheads in the turquoise water below.
Actionable Tips for Driving the Bridges
If you're planning this trip, don't just floor it to Key West. You’ll miss the best parts.
Check the Wind Forecast.
Driving the Seven Mile Bridge in a high-profile SUV during a 25 mph crosswind is a workout. Your arms will be sore from fighting the steering wheel.
Stop at Bahia Honda State Park.
Just past the Seven Mile Bridge (around Mile Marker 37), you’ll find the Bahia Honda Rail Bridge. It’s one of the most photographed spots in Florida. You can walk up onto a section of the old bridge and look down at the white sand beaches. It’s the best view in the entire island chain.
Mind the Mile Markers.
Everything in the Keys is located by "MM." If you’re looking for a restaurant and they say they're at MM 82, they’re 82 miles from Key West. It’s the only way people navigate down there.
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Avoid Friday Afternoon/Sunday Evening.
The traffic "bottleneck" is real. Everyone from Miami heads down on Friday and leaves on Sunday. If you can, drive the bridges on a Tuesday morning. It’s like having a private highway through the Caribbean.
Fuel Up in Florida City.
Gas prices jump significantly once you cross the "18-Mile Stretch" into Key Largo. Fill your tank on the mainland to save twenty bucks.
The bridges to the Florida Keys aren't just roads; they're engineering miracles that probably shouldn't exist given the hurricanes that roll through every few years. Driving them is a rite of passage for any Florida traveler. Just take your time, watch for the "Old Seven" on your right, and remember: it's 6.79 miles, not seven.