Between December 1931 and the end of 1933, DSHD constructed a causeway across of the marsh on the east bank of the river, a process that required multiple applications of fill dirt and dynamite to create a stable surface for a modern highway. A Scherzer rolling lift bascule bridge with a clear opening was constructed across the St. Jones River in 1933 and 1934. Bay Road was widened and the new sections of highway were built with concrete pavement starting in 1934. The new highway was constructed with provisions for later being expanded to a divided highway. US 113 was relocated to the Dover Bypass, which was also known as the Eastern Boulevard, north to US 13 (State Street) when the new highway opened by the last weekend of May 1935. DuPont Highway between Little Heaven and Dover and State Street in Dover were designated US 113 Alternate.