So many roads named after something or named some nostalgic but generic thing, that no one realizes when they are actually driving on the modernized version of the real thing.

Among other things, it seems most expect there to be a route 66 style or (american) rail-row insitu abandoned artifact of these roads (which do sometimes exist in stretches of realignment) but don't realize that un-abandoned places generally aren't going to abandon their roads.

ETA: Old Spanish Trail went from the Atlantic coast of Florida to the Pacific along the Gulf Coast then continued west. But the places with continuous use to today from Texas east are now more often excluded from 'Old Spanish Trail' maps.