The Yokosuka-Yokohama section was designated as National Highway 45 on 8 July 1887 and became National Highway 31 in 1920 and Route 16 in 1952.
On July 8, 1887, the Yokosuka-Yokohama section was designated as National Highway 45; it changed to National Highway 31 in 1920 and became Route 16 in 1952.