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A paving train near Memphis, Tenn., in 1929. Steel forms were set ahead of time on the subgrade to hold the concrete in place.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/America%27s_Highways_1776%E2%80%931976_-_page_452b.jpg/300px-America%27s_Highways_1776%E2%80%931976_-_page_452b.jpg)
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.
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