Few if any signs are present in Louisiana, but the route has been defined by state law. It begins at Venice on the west bank, following LA 23 into Gretna, where the eastern route splits. The western route, historically part of the National Route here, turns west on LA 18, which it follows all the way to Donaldsonville except for a detour on LA 541 from Harvey to Bridge City. A short piece of LA 1 connects the Great River Road to LA 405, which hugs the river to another junction with LA 1 in Plaquemine. LA 988 loops off LA 1 from northern Plaquemine back to yet another junction south of Port Allen, where the route leaves LA 1 again on Oaks Avenue, which becomes LA 987-5 and turns north along the river on River Road. LA 987-4 (Court Street) leads back west to Jefferson Avenue, which the Great River Road follows north to LA 986 along the river and under the Huey P. Long Bridge (US 190), which carries the National Route to the east bank (with access via LA 987-1).