US 98 begins at a junction with FL A1A in Palm Beach, or at US 1 in West Palm Beach. It then passes through West Palm Beach, Bartow, Lakeland, Panama City, Destin, Ft. Walton Beach, and Pensacola on its way north and west out of the state. US 98 began as a Florida-only US highway, stretching along the NW coast of the state.
More details are on the history page.
I expect the Palm Beach signs will be replaced with FL 80 signs once their service life has expired. Between Chassahowitska and Clinton Heights, US 98 is becoming part of the outer growth of Greater Tampa Bay, and is to have an interchange with the Suncoast Parkway. The original route of US 98, it passes through Panama City Beach, then Open Sands, Laguna Beach, Sunnyside, to US 98 at Hollywood Beach. The beach strip of the 'Redneck Riviera' with little 'exit' signs leading to the former Bypass route, which is now the mainline. Lots of touristy stuff, hotels and gift shops, if you like that kind of thing.