In 1935, US 301 was extended southwest to US 15 at Summerton. This extension took it west on US 76 (formerly US 17) to Florence and south on US 52 (also formerly US 17) to Effingham. There it split to the southwest, running along what had been SC 4 via Manning to Summerton.[citation needed] This again travels parallel to I-95.
In the late 1940s, US 301 was extended again, south all the way towards Tampa, Florida. On the way there from South Carolina it ran along US 15 southwest to Santee, South Carolina and replaced SC 4 west to Orangeburg. From Orangeburg, US 301 ran southwest with U.S. Route 601 to Bamberg, replaced SC 33 to Ulmer, replaced SC 508 to Allendale, and replaced SC 73 to the Georgia state line.[citation needed] When I-95 was built across Lake Marion in 1968,[8] US 301 and 15 traveled parallel to it until they were relocated in a triple concurrency in 1987.[9] In 2007, US 301 was rerouted on new 7.51-mile (12.09 km) bypass routing southeast of Florence.[10]
U.S. Route 217 (US 217) was an original U.S. Highway, established in 1927. A renumbering of SC 23, it traversed from US 17, in Pee Dee, north through Latta and Dillon before entering North Carolina. In 1932, the entire route was renumbered as US 301.
^Special Committee on U.S. Route Numbering (December 4, 1987). "Route Numbering Committee Agenda" (Report). Washington, DC: American Association of State Highway and Transportation Officials. p. 3 – via Wikisource.
^Special Committee on U.S. Route Numbering (May 5, 2007). "Report of the Special Committee on U.S. Route Numbering"(PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. p. 6. Archived from the original(PDF) on October 16, 2017. Retrieved April 15, 2014.