U.S. Route 13 or U.S. Highway 13 (US 13) is a north–south United States Numbered Highway established in 1926 that runs for 518 miles (834 km) from Interstate 95 (I-95) just north of Fayetteville, North Carolina, to US 1 in the northeastern suburbs of Philadelphia, Pennsylvania, near Morrisville. In all, it traverses five states in the Atlantic coastal plain region. It follows the Atlantic coast more closely than does the main north–south U.S. Highway of the region, US 1. Because of this, its number is out of place on the general U.S. Highway numbering grid, as it should be running west of US 11 but does not. Its routing is largely rural, the notable exceptions being the Hampton Roads area in Virginia and the northern end of the highway in Delaware and Pennsylvania. It is also notable for being the main thoroughfare for the Delmarva Peninsula and carrying the Chesapeake Bay Bridge–Tunnel to it in Virginia.
US 13's original plan in 1926 had the route serve no further south than the Delmarva Peninsula. However, it has been extended many times, connecting to the mainland via ferry service and eventually reaching North Carolina. This link across the mouth of the Chesapeake Bay became fixed in 1964 with a bridge–tunnel. The entire route on the Delmarva Peninsula, except for a few sections in Accomack County, Virginia, has been dualized fully with four lanes, and further upgrades continue, such as a freeway section around the east side of Salisbury, Maryland.
