Complex sentence: Many of the original bridges were replaced during the 1980s, following Flagler's dream, the Overseas Highway (U.S.1, which runs from Key West to Fort Kent, Maine) continues to provide a highway link to Key West.
Split into simpler sentences: Many of the original bridges were replaced during the 1980s. The Overseas Highway (U.S.1, which runs from Key West to Fort Kent, Maine) continues to provide a highway link to Key West.