The Isaiah David Hart Bridge is a truss bridge that spans the St. Johns River in Jacksonville, Florida. It carries U.S. Route 1 Alternate and State Road 228 (SR 228). It is named after Isaiah Hart, the founder of Jacksonville and is often referred to as the Hart Bridge. It was designed by Sverdrup & Parcel. The Hart Bridge is one of the longest truss bridges in the world, and has the world's third longest main span of any truss bridge.