You’re driving south of Miami, the air starts smelling like salt and coconut suntan lotion, and suddenly the land just... stops. Ahead of you lies a thin ribbon of concrete stretching into an impossible shade of turquoise. If you’ve ever wondered how long is the bridge to key west, you’re actually asking about a massive engineering feat that isn't just one single bridge. It’s 42 of them.
People get confused. They hear "Seven Mile Bridge" and assume that’s the whole journey. Not even close. To get from the mainland to the Southernmost Point, you’re traversing over 100 miles of the Overseas Highway, which is technically U.S. Route 1. It’s a surreal experience where you feel like you're driving on water. Honestly, it’s a bit unnerving the first time the guardrails disappear and you’re surrounded by nothing but the Atlantic Ocean and the Gulf of Mexico.
The Famous Seven Mile Bridge: The Heavy Lifter
Let’s talk about the big one. When people ask how long is the bridge to key west, they are usually picturing the Seven Mile Bridge. It’s the crown jewel of the Florida Keys.
Surprisingly, it isn't exactly seven miles long. If we’re being pedantic—and engineers usually are—the "new" bridge, which opened in 1982, is actually 6.79 miles long. It connects Knight's Key in the Middle Keys to Little Duck Key in the Lower Keys. It’s a massive span of segmental concrete that rises 65 feet in the air at its highest point to let boats pass underneath.
Driving it feels endless.
On your right, you’ll see the rusted, narrow remains of the "Old Seven," the original bridge built by Henry Flagler for his Overseas Railroad. It’s a ghost of the past. Seeing the two bridges side-by-side really puts into perspective how much we’ve progressed in construction, but also how insane Flagler must have been to try building a railroad out here in 1905.
Why the length matters for your trip
If you’re timing your drive, the Seven Mile Bridge takes about 8 to 10 minutes to cross at the 55 mph speed limit. Don't speed. The Monroe County Sheriffs are notoriously vigilant on this stretch. Plus, why would you want to rush? The view is the whole point. You’ve got emerald waters, occasional leaping rays, and the terrifying realization that there is nowhere to pull over if you have a flat tire.
Total Distance: The 113-Mile Reality
The Overseas Highway starts at Mile Marker 113 at the Florida City/Key Largo line. Key West is Mile Marker 0.
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So, while the Seven Mile Bridge is the longest individual span, you are essentially "bridging" the gap between islands for over 100 miles. Some bridges are tiny—just a few dozen feet over a narrow canal. Others, like the Bahia Honda Bridge or the Long Key Bridge, are significant landmarks in their own right.
The Long Key Bridge is actually the second-longest in the chain, stretching for about 2.3 miles. It’s beautiful in a different way, with a low profile that makes you feel like you’re skimming the surface of the waves.
A History Born of Hubris and Hurricanes
You can't talk about the length of these bridges without mentioning the 1935 Labor Day Hurricane. It remains one of the most intense storms to ever hit the United States. It basically wiped Flagler’s railroad off the map.
The tracks were twisted like pretzels.
The state of Florida eventually bought the right-of-way and the remaining bridge structures from the bankrupt Florida East Coast Railway. They paved over the old railroad bridges to create the first version of the Overseas Highway. If you look closely at some of the older, retired bridges that still stand as fishing piers, you can see the original railroad architecture. It’s rugged. It’s heavy. It’s built of concrete and grit.
Engineering the "New" Bridges
By the late 1970s, the old railroad-turned-car-bridges were falling apart. They were narrow and terrifying. If two trucks passed each other, drivers would instinctively pull their side mirrors in.
The federal government poured hundreds of millions of dollars into the "new" Overseas Highway project between 1979 and 1982. This gave us the modern spans we use today. These bridges aren't just long; they are built to withstand 200 mph winds and the relentless corrosive power of salt spray. They used a "pre-cast" method where giant segments were made on land and then hoisted into place by barges. It was like LEGO for giants.
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Navigating the Drive: Practical Realities
Knowing how long is the bridge to key west is only half the battle. The other half is timing.
Traffic in the Keys is a binary system: it’s either moving perfectly or it is a complete standstill. Because it’s a two-lane highway for the vast majority of the trip, one fender bender on the Seven Mile Bridge can back up traffic for three hours. There are no side roads. There is no "taking the back way." You are on a literal island chain.
- Weekends are brutal. If you leave Miami on a Friday afternoon, expect to double your travel time.
- Deer Key is a bottleneck. The speed limit drops to 35 mph (and lower at night) to protect the endangered Key Deer. Don't ignore this.
- Fuel up in Homestead. Gas prices jump significantly once you cross into Key Largo and stay high until you hit Key West.
Surprising Facts About the Spans
Most people assume the bridges are just flat roads, but the variety is actually wild.
- The Nile of the West: Some early travelers called the Seven Mile Bridge the "Eighth Wonder of the World."
- Movie Magic: You’ve probably seen these bridges before. The Seven Mile Bridge was famously used in True Lies (where they "blew up" a segment, though it was actually a miniature model) and 2 Fast 2 Furious.
- The Highest Point: The bridge over Channel 5 is surprisingly high, but the highest point on the actual road is the "hump" of the Seven Mile Bridge, designed to let tall masts through.
- The Old Seven Walkway: You can actually walk or bike on a restored section of the Old Seven Mile Bridge now. It leads to Pigeon Key, a tiny island that served as a base camp for railroad workers. It’s a 2.2-mile trek one way, and it’s arguably the best photo op in the state.
What Most People Miss
The bridge to Key West isn't just a way to get to the bars on Duval Street. It's an ecological transition zone. As you move across these spans, you’re crossing over the Florida Keys National Marine Sanctuary.
You’re literally driving over coral reefs and seagrass beds that support one of the most diverse ecosystems on the planet. I’ve seen sea turtles from my car window while stuck in traffic on the Channel 5 bridge. It makes the wait a lot more bearable.
Actionable Tips for the Overseas Highway
If you're planning this drive, don't just put your head down and floor it.
Check the wind. If winds are over 25-30 mph, the long bridges can be sketchy for high-profile vehicles like RVs or Jeeps with soft tops. You’ll feel the car swaying. It’s not fun.
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Download your maps. Cell service is surprisingly spotty between the islands. Once you’re in the middle of a five-mile bridge, your GPS might decide to take a nap.
Stop at Fred the Tree. On the old Seven Mile Bridge, there is a famous Australian Pine growing right out of the concrete. Locals decorate it for holidays. It’s a symbol of the resilience of the Keys.
Time the sunset. If you can be on the Seven Mile Bridge or the Long Key Bridge during "Golden Hour," do it. The reflection of the orange sky on the water on both sides of the car makes it feel like you’re flying through a painting.
Plan for the "Bridge Run." Every April, the Seven Mile Bridge closes for a few hours for a massive 1,500-runner race. If you’re visiting then, check the schedule or you’ll be sitting in your car for a very long time.
Ultimately, the bridge to Key West is 113 miles of history, 42 engineering marvels, and one very long, very beautiful stretch of asphalt that reminds you just how small we are compared to the ocean.
Next Steps for Your Florida Keys Road Trip:
- Check the Florida Department of Transportation (FDOT) live cams specifically for the Seven Mile Bridge before you leave Homestead; this will tell you if there’s a wreck causing a multi-hour delay.
- Mark "Pigeon Key" on your GPS as a stopping point. It’s the only way to experience the "old" bridge on foot and understand the sheer scale of what was built 100 years ago.
- Monitor the weather via the National Weather Service Key West office rather than generic apps, as they provide specific marine-based forecasts that account for bridge wind speeds and sudden squalls.