 In 1937, the route was extended east to US 30 in Coatesville by heading east along its current route to Wagontown and turning south to Coatesville, with PA 897 replacing the former route between White Horse and Gap.By 1940, the route was extended west to US 22 in Harrisburg, heading west to Marietta, north to Hershey, northwest to Union Deposit, and west to Harrisburg.PA 340 was rerouted to end at US 30 in Thorndale during the 1940s.