The state highway between US 13 and Gumboro was fully complete the following year. By 1936, the road between Millsboro and Gravel Hill was paved. DE 30 was first designated in 1936 to run from DE 20 in Seaford north and east to DE 404 northwest of Bridgeville, heading north and crossing DE 18 in Atlanta before turning east to reach DE 404. This was eliminated by 1938, and is now Atlanta Road and Dublin Hill Road. By 1938, DE 30 was designated to run from DE 24 in Millsboro north to DE 5 in Milton, following its current alignment to north of Gravel Hill and then running along Shingle Point Road north into Milton. A portion of current DE 30 south of the DE 16 intersection was paved a year later. By 1952, the current route of DE 30 north of Gravel Hill was paved. DE 30 was rerouted to follow its present alignment north to DE 14 (now DE 1) south of Milford by 1971. By 1994, DE 30 was extended from Millsboro to its current terminus at Bi-State Boulevard. The northern terminus of DE 30 was moved to its current location at DE 1 Bus. by 2003 when a road connecting DE 30 to DE 1 Bus. was completed. In November 2012, construction began on an interchange at DE 1 southeast of Milford. The interchange between DE 1 and DE 30 was completed in July 2014. On February 29, 2016, construction began on a superstreet intersection at US 13; this project was completed on May 19 of that year. Delaware Route 30 Alternate (DE 30 Alt.) was a  alternate route of DE 30 south of the city of Milford in the Cedar Creek area. It ran from DE 30 northeast to DE 1 along two-lane undivided Johnson Road, passing through a mix of farmland, woodland, and residential development. The route was created by 1999. DE 30 Alt. originally had full access to and from DE 1, but the median crossover was modified in 2011 to only allow access from DE 30 Alt. to southbound DE 1 while retaining access to DE 30 Alt. from both directions of DE 1. The DE 30 Alt. designation was removed from the road by 2017.