The section of the route between Mount Holly Springs and Carlisle became a turnpike called the Hanover and Carlisle Turnpike in 1812, which connected Carlisle to Hanover and served as a trade link between the Cumberland Valley and Baltimore. PA 34 was designated in 1928 to run from US 15 (now US 15 Bus.) in Gettysburg north to US 11 in Carlisle. The same year, the road between Carlisle and Mecks Corner was designated PA 33 while the road between Mecks Corner and Newport became part of PA 5. PA 34 was extended north from Carlisle to US 22 (Juniata Parkway) east of Newport in 1937, replacing those sections of PA 33 and PA 5. For a short time in the 1960s, PA 34 extended south from Gettysburg to US 15 in Fairplay along a former alignment of US 15 before being replaced by US 15 Bus. In 1970, the route was extended north from Newport to US 11/US 15 south of Liverpool.