Driving the last spike
Interesting, found this on Wikipedia
In December 1838, construction started. Work was divided into six sections; access to each was via a 25-foot-diameter (7.6 m) ventilation shaft, which ranged in depth from 70 feet (21 m) at the eastern end to 300 feet (91 m) towards the western end.
[7] The men, equipment, materials and 247,000 cubic yards (189,000 m3) of extract had to go in and come out of the shafts assisted by
steam-powered winches. The shafts were the safety exits from the tunnel.
[7]
