 In 1911, the Sproul Road Bill defined Legislative Route 181 for the segment between Washington and West Newton, LR 186 between West Newton and Somerset, LR 364 between Somerset and Dividing Ridge, and LR 49 between Dividing Ridge and Bedford.The PA 31 designation began appearing on road maps and signage in 1927.At that time, the western terminus was at the West Virginia line at West Virginia Route 27.