A drilling crew poses for the above photo in 1931. To create the Hawks Nest Tunnel, workers had to drill through nearly pure sandstone, which kicks up toxic silica dust. Workers in the photo are not wearing respirators — a requirement later mandated by Congress after hundreds of men died from exposure to silica in the tunnel.

A drilling crew poses for the above photo in 1931. To create the Hawks Nest Tunnel, workers had to drill through nearly pure sandstone, which kicks up toxic silica dust. Workers in the photo are not wearing respirators — a requirement later mandated by Congress after hundreds of men died from exposure to silica in the tunne