The Seven Mile Bridge is a famous bridge in the Florida Keys, in Monroe County, Florida, United States. It connects Knight's Key (part of the city of Marathon, Florida) in the Middle Keys to Little Duck Key in the Lower Keys. Among the longest bridges in existence when it was built, it is part of the Overseas Highway in the Keys, which is part of the 2,369-mile U.S. Route 1.There are two bridges in this location. The modern bridge is open to vehicular traffic; the older one only to pedestrians and cyclists. The older bridge, originally known as the Knights Key-Pigeon Key-Moser Channel-Pacet Channel Bridge, was constructed from 1909 to 1912 under the direction of Henry Flagler and Clarence S. Coe as part of the Florida East Coast Railway's Key West Extension, also known as the Overseas Railroad.HistoryAfter the railroad was damaged by the Labor Day Hurricane of 1935, the line was sold to the United States government, which refurbished Seven Mile Bridge for automobile use. Unsupported sections were added in 1935 to widen it for vehicular traffic. Dismantled trackage was recycled, painted white, and used as guardrails. It had a swing span to allow passage of boats in the Moser Channel of the Intracoastal Waterway, near where the bridge crosses Pigeon Key, a small island that held a work camp for Flagler's railroad. Hurricane Donna in 1960 caused further damage.