US 15A was formed no later than 1936. Depending on which map you believe, it was either a completely new route or replaced a seminal US 401 south of Raleigh and NC 13 north of Raleigh. In any case, once 15A was definitively established, it ran nearly across the entire state, from Creedmoor all the way south to Laurinburg.

Aside from a couple of reroutings in downtown Raleigh (matters of a few blocks here and there), 15A never saw any changes, except for being moved off Old Creedmoor Road sometime around 1950. It was decommissioned and replaced by US 401 (again?) south of Raleigh and NC 50 north of Raleigh in 1956.