In the 1950s and 1960s, about three-quarters of the Oroville-Chico Highway was absorbed by other routes. A new two-lane alignment of U.S. Route 99E (Legislative Route 3, now SR 99) between east of Richvale and Chico opened in the mid-1950s, using part of the Oroville-Chico Highway south of Durham Dayton Highway and bypassing the remainder to the junction south of Chico. In the early 1960s, U.S. Route 40 Alternate (Legislative Route 21, now SR 70) was relocated due to the damming of Lake Oroville across its old alignment. The bridge over the West Branch Feather River northwest of the dam opened in August 1962, resulting in US 40 Alt. using the Oroville-Chico Highway (which was relocated to a new four-lane freeway alignment) south of Wicks Corner. The remainder, which was never part of a sign route, became Route 149 in the 1964 renumbering.