The first divided highway project on US 113 proper began in 1957. The U.S. Highway's second carriageway was completed from its junction with US 13 and South Little Creek Road to the southern end of Dover Air Force Base in 1959. The first segment of the original DuPont Highway south of Dover to be expanded to a divided highway was from Walnut Street at the north end of Milford to south of Frederica; the southbound roadway of the divided highway section was constructed between 1957 and 1959. The US 113 divided highway was extended around Milford when the southbound carriageway was built from Walnut Street south to near Lincoln between 1961 and 1963; the project included a pair of bridges over the east end of Haven Lake at the Kent–Sussex county line. The Frederica bypass was constructed as a four-lane divided highway between 1963 and 1965. US 113 was expanded to a divided highway from just north of the Maryland state line in Selbyville to DE 20 north of Dagsboro between 1965 and 1967. The highway's second carriageway was built from north of Dagsboro to Stockley between 1966 and 1968. US 113 was completed as a divided highway from Stockley to Bedford Street on the northern edge of Georgetown in 1969. US 113's partial interchange with the Milford Bypass opened in 1971.