What Seven Mile Bridge Is and Where It Stands

Seven Mile Bridge is a 6.79-mile concrete bridge in the Florida Keys that connects Marathon to Bahia Honda Key. It carries US Route 1 (the Overseas Highway) across open water between two islands. The bridge opened to traffic in 1982 and replaced an earlier bridge built on the same route in 1912. Today it is one of the most photographed bridges in the United States, partly because of its height, length, and the unobstructed ocean views from both directions.

The bridge sits roughly 65 miles south of Miami and about 160 miles north of Key West. Drivers heading to the southernmost Keys must cross it; there is no alternate route. On clear days, the view extends to the horizon in all directions. On foggy or stormy days, the bridge can feel isolated and exposed.

Key Takeaways

  • Seven Mile Bridge opened in 1982 and carries US Route 1 across open water between Marathon and Bahia Honda Key in the Florida Keys.
  • The bridge is 6.79 miles long and rises 65 feet above the water at its highest point, making it one of the longest bridges over water in the continental United States.
  • The original bridge, built in 1912 as part of Henry Flagler's Overseas Railroad, still stands parallel to the current bridge and is now a pedestrian and bicycle path.
  • Crossing the bridge takes roughly 10 to 12 minutes by car under normal conditions, though weather and traffic can extend that time significantly.
  • The bridge is a major landmark for tourists and a critical transportation link for residents of the lower Florida Keys.

The Original Bridge and Henry Flagler's Railroad

The first bridge on this route was part of Henry Flagler's Overseas Railroad, a rail line that extended from Miami to Key West between 1906 and 1912. Flagler was a Standard Oil co-founder who invested in Florida development. His railroad was an engineering feat for its time: it required building bridges, causeways, and embankments across open ocean and shallow water where no infrastructure had existed before.

The original Seven Mile Bridge was a steel railroad bridge completed in 1912. It carried passenger and freight trains across the gap between Marathon and Bahia Honda. The railroad operated until 1935, when a major hurricane damaged much of the line. After the hurricane, the railroad was abandoned, and the right-of-way was sold to the state of Florida.

The original bridge structure still stands today, running parallel to the modern bridge. It was converted to a pedestrian and bicycle path in 1982, the same year the new bridge opened. Walkers and cyclists can cross the old bridge on foot, though the experience is different from driving: the views are closer to the water, and the bridge feels narrower and more exposed.

Engineering of the Modern Bridge

The current Seven Mile Bridge was designed to carry automobile traffic on the Overseas Highway. It is a segmental concrete bridge, meaning it was built in sections that were assembled and connected together. The bridge rises 65 feet above the water at its highest point, allowing boats to pass underneath. The deck is wide enough for two lanes of traffic in each direction, with a median barrier separating them.

Construction began in 1978 and took four years to complete. The bridge was built in segments that were floated into place and then connected. This method allowed construction to proceed without blocking the old bridge, which remained open to traffic during the build. The total cost was approximately $44 million in 1982 dollars.

The bridge is exposed to salt water, high winds, and intense sun. Maintenance is ongoing: the concrete is sealed and inspected regularly, and the bridge is repainted periodically. Hurricanes are a constant concern; the bridge is designed to withstand winds up to 150 miles per hour, though major storms can still cause temporary closures.

Crossing the Bridge: Time, Traffic, and Conditions

Driving across Seven Mile Bridge takes roughly 10 to 12 minutes under normal conditions. The speed limit is 55 miles per hour, though traffic often moves slower during peak tourist season (November through March). The bridge has no shoulders, so disabled vehicles must be towed off; there are no rest areas or pull-offs on the bridge itself.

Weather affects crossing time and safety. Fog can reduce visibility to a few hundred feet, making the bridge feel claustrophobic despite its length. High winds can push vehicles, especially tall ones like RVs and trucks. Rain is common in the Keys, and wet pavement reduces traction. During hurricane season (June through November), the bridge may close if sustained winds exceed certain thresholds or if a major storm approaches.

Traffic congestion happens during holidays and weekends, particularly in winter. The bridge is a single route with no bypass, so any accident or disabled vehicle can back up traffic for miles. Local residents and frequent visitors often cross early in the morning or late in the evening to avoid crowds.

What You See From the Bridge

The bridge offers views of open Atlantic Ocean on the north side and the Gulf of Mexico on the south side. On clear days, the water is turquoise or deep blue depending on depth and light. The horizon is unobstructed in all directions, which creates a sense of being suspended over water. At sunrise and sunset, the light changes the color of the water and sky dramatically.

Marine life is visible from the bridge. Dolphins are common, especially in the early morning. Manatees appear occasionally in the shallower areas near the Keys. Fish jump in the water below. Seabirds—pelicans, frigatebirds, herons—are present year-round. During certain seasons, sea turtles can be spotted in the water.

The old bridge is visible from the new one, running parallel a short distance away. The contrast between the two structures is striking: the old steel railroad bridge looks delicate and industrial, while the modern concrete bridge is massive and smooth. Photographers often stop at the rest areas on either end of the bridge to capture both structures together.

Pedestrian and Bicycle Access on the Old Bridge

The original Seven Mile Bridge is open to pedestrians and cyclists during daylight hours. Access is free. The old bridge is narrower than the new one and has no vehicle traffic, making it quieter and more peaceful. The walk or ride takes 30 to 45 minutes depending on pace and how often you stop to look at the view.

The old bridge has no shade, no water fountains, and no facilities. On hot days, the sun reflects off the steel and concrete, making it significantly hotter than the surrounding air. Cyclists should bring water and wear sunscreen. The bridge is exposed to wind, which can be strong, especially on the Gulf side.

Access points are at Marathon on the north end and Bahia Honda Key on the south end. Parking is available at both ends, though spaces fill quickly during peak season. The old bridge is popular with photographers, especially at sunrise and sunset, so expect crowds during those times.

Visiting and Practical Information

Seven Mile Bridge is on US Route 1, which is the main highway through the Florida Keys. There is no entrance fee to cross the bridge by car or to walk or bike on the old bridge. The bridge is open 24 hours a day, though weather may cause temporary closures.

Rest areas and viewing areas are located at both ends of the bridge. On the Marathon side (north), there is a small rest area with parking and a scenic overlook. On the Bahia Honda side (south), Bahia Honda State Park offers parking, facilities, and beach access. Both areas are good places to stop, take photos, and stretch before continuing.

The bridge is a popular stop for road-trippers and tourists heading to Key West. Many people stop specifically to photograph the bridge or to walk or bike the old bridge. If you are traveling during peak season, plan to arrive early or late in the day to avoid crowds and heat.

Frequently Asked Questions

How long does it take to drive across Seven Mile Bridge?

Under normal traffic conditions, driving across takes 10 to 12 minutes at the 55 mph speed limit. During heavy traffic or bad weather, it can take 20 to 30 minutes. The bridge has no shoulders or pull-offs, so you cannot stop in the middle.

Can I walk or bike on the new bridge?

No. The new bridge is for vehicles only. Pedestrians and cyclists must use the old bridge, which runs parallel and is open during daylight hours. The old bridge walk takes 30 to 45 minutes.

Is the bridge closed during hurricanes?

Yes. The bridge closes when sustained winds exceed certain thresholds or when a major hurricane approaches. Closures are announced by the Florida Department of Transportation. During hurricane season, check conditions before traveling.

Where can I park to photograph the bridge?

Rest areas at both ends of the bridge have parking and scenic overlooks. Bahia Honda State Park on the south end has more extensive parking and facilities. The old bridge also has parking areas at both access points.

What is the difference between the old and new bridges?

The old bridge (1912) is a steel railroad bridge now used for pedestrians and cyclists. The new bridge (1982) is a concrete highway bridge for vehicles. Both are visible from each other and offer different perspectives of the same crossing.