Work on paving the Ridge Route with thick reinforced concrete began in 1917, but was delayed until 1919 by the U.S. entry into World War I. During work on the road, traffic was detoured via Mint and Bouquet Canyons. The road reopened on November 15, 1919, completely paved except north of Lebec, including the grade at Grapevine, which was only oiled. After a bond issue was passed in July 1919, this portion was paved from September 1919 to May 1921; the dangerous detour during the paving included a 20 percent grade. The paving added about $1 million to the cost, for a total price of about $1.5 million (about $ in ), which was not paid off until 1965. Asphalt was added on top of the concrete for south from Swede's Cut in 1922, and in 1924 a number of blind curves were widened and straightened.