In 1950, recommendations were made by the chief engineer of the DSHD to widen US 13 into a divided highway between Delmar and Dover. The divided highway was completed from Hearne's Mill north to just south of Greenwood in 1952. The highway bypassed Bridgeville to the east, rerouting US 13 off Main Street in that town. In 1953, the divided highway portion of US 13 was built around Seaford. The divided highway was completed between the Maryland border in Delmar and Hearne's Mill and from Harrington to Dover in 1954. The new alignment of US 13 between Delmar and Hearne's Mill was built further to the east, with the former two-lane alignment running through Delmar, Laurel, Blades, and Seaford becoming US 13 Alt. The bypassed two-lane alignment between Canterbury and Camden was also designated as US 13 Alt. In 1956, work was underway in widening US 13 into a divided highway between south of Greenwood and Harrington. The widening of this portion of US 13 was finished in 1957, completing widening US 13 to a divided highway between Delmar and Wilmington. By 1957, the former alignment of US 13 in Bridgeville along Main Street was designated US 13 Alt. (now US 13 Bus.) while US 13 Alt. between Delmar and Hearne's Mill was decommissioned.