The highway crosses the Big Pee Dee River, at one time passing through an old covered bridge, the only one on US 1 . Each piece of wood was cut and numbered, its place being determined in advance of the building. During the extreme high water of the spring floods the bridge is impassable The Great Pee Dee is large and wild. Most of the land bordering the river is floodplain forest. The corridor is a 70-mile by 3-mile swath of high quality wildlife habitat, boasting 120 species of fish, at least 25 rare plant species, several endangered and threatened species (including the American alligator, red-cockaded woodpecker, bald eagle and swallow-tailed kite), 17 species of duck (all but the wood duck are migratory visitors), a number of wading birds and fur bearing species, and typical South Carolina game species, such as white tail deer and turkey. River travelers will notice a distinct change in the Great Pee Dee’s character as they go from the US 378 Bridge to Winyah Bay. Cypress-tupelo and bottomland hardwood forests, with hairpin meanders, sandy point bars and many interconnected oxbow lakes surround the upper portions of the river. Abandoned channels of the river, often called “lakes” (e.g., Jordan Lake, Thomas Lake), can be explored in small boats. Below the confluence with the Little Pee Dee (another adjoining State Scenic River), the sandy point bars and banks disappear. The surrounding forest becomes tidal swamp. The main forest species are still present, but some, like the swamp and black willows that dominate sandy banks upstream, vanish completely. A final transition happens below Thoroughfare Creek, where the freshwater tidal marshes, once cultivated as part of antebellum rice plantations, begin to displace the tidal swamp forest.