U.S. Route 13 Business is an 8.19-mile (13.18 km) business route of US 13 that runs through the heart of the city of Wilmington in New Castle County, Delaware, where US 13 bypasses downtown Wilmington to the east, running near Interstate 495 (I-495) and the Delaware River. US 13 Bus. begins at I-495 and US 13 at the southern border of Wilmington and heads north toward the downtown area, where it splits into a one-way pair. Past downtown, the business route heads through the northeastern part of the city on North Market Street before continuing through suburban Brandywine Hundred on Philadelphia Pike. US 13 Bus. reaches its northern terminus at US 13 in Claymont. US 13 Bus. is a four-lane road for much of its length.

U.S. Route 13 (US 13) is a U.S. highway running from Fayetteville, North Carolina, north to Morrisville, Pennsylvania. In the U.S. state of Delaware, the route runs for 103.33 mi (166.29 km). It traverses the entire north–south length of the state from the Maryland state line in Delmar, Sussex County, north to the Pennsylvania state line in Claymont, New Castle County. US 13 connects many important cities and towns in Delaware, including Seaford, Dover, and Wilmington. The entire length of US 13 in Delaware is a multilane divided highway with the exceptions of the segment through Wilmington and parts of the route in Claymont. Between the Maryland state line and Dover, US 13 serves as one of the main north–south routes across the Delmarva Peninsula. From Dover north to Tybouts Corner, the route is followed by the controlled-access Delaware Route 1 (DE 1) toll road, which crosses the route multiple times and has multiple interchanges with it. US 13 bypasses downtown Wilmington to the east before it heads northeast of the city parallel to Interstate 495 (I-495) and the Delaware River to Claymont. US 13 is the longest numbered highway in the state of Delaware.