The Seven Mile Bridge is a bridge in the Florida Keys, in Monroe County, Florida, United States. It connects Knight's Key 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.