Engineers and workers began boring through the east and west ends of Hoosac mountain to build the Hoosac Tunnel in Northwestern Massachusetts. Shoddy engineering resulted in a false start on the eastern end in 1852. This postcard shows the relocated east entrance to the tunnel. Work delays plagued the project in its early years, and early drilling and blasting technology proved inadequate. Workmen had succeeded in digging only 20% of the 4.75-mile tunnel by 1864. New technologies and a revised work plan rescued the project. Engineers mounted as many as six of inventor Charles Burleigh’s new compressed air drills on a carriage to speed drilling. Workmen began blasting with trinitroglycerin (TNT), a highly unstable explosive 13 times more powerful than the black gunpowder used previously. Work still proceeded slowly, due to the difficulty of blasting through mica, slate, and quartz, groundwater leaking into the tunnel, and a severe fire. It took three shifts of 700 men working six days a week to finish the 24-foot diameter tunnel in 1874.