US Highway 1, locally known as the Overseas Highway, runs 120 miles along the island chain and is 2 lanes most of the way.  Several 4-lane sections gets up to 55 mph but the normal speed limit is 45.  It crosses numerous bridges including a seven mile long span and the one pictured here that's 3 miles long and connects Long Key to Grassy Key.  Conveniently, everything is addressed by its corresponding mile marker.

There are 4 distinct areas, starting with Key Largo in northeast, and moving southwest to Islamorada, Marathon, and finally, Key West.