The A68 originally started on the A7 in central Edinburgh, running southeast towards Dalkeith. The A7 was rerouted this way as far as the Sheriffhall Roundabout in the late 1990s, truncating the start of the A68 back to this junction.
In 2008, a northern bypass of Dalkeith was built, which changed the start of the A68 to a new grade-separated roundabout with the A720. The old road through the town is now an extension of the A6106.
In conjunction with the A696, the A68 formed part of a trunk road between Edinburgh and Newcastle. The English section of this route was detrunked in 2004. The entirety of the A68 within Scotland remains a trunk road and is maintained to a greater standard.
A68 historic route from 1922/3 numbering
Prior to the construction of the Corbridge bypasses, the A68 ran straight through the centre of town, multiplexing with the A69 along the section of road that could least bear it: the narrow 16th-century bridge across the Tyne. A69 traffic was taken out of town in 1977 when the northern bypass was built, then in 1982 the eastern bypass was opened, taking on the A68 number, giving the road its current route and multiplex along the A69 (which had always been the dominant number in the area). The former A68 through Corbridge is now the B6529, followed by the A695 to Riding Mill. After meeting the original western end of the A695 the A68 left town along Whiteside, which has no connection to the current A68 for vehicular traffic.