Page:America's Highways 1776–1976.djvu/458

 A paving train near Memphis, Tenn., in 1929. Steel forms were set ahead of time on the subgrade to hold the concrete in place.

Excavation work on the Blue Ridge Parkway in 1936. In the background men drill holes for explosives used to break up rock, while a diesel-powered shovel loads earth into dump trucks. 452