The class E-1 of the Erie Railroad consisted of 29 Atlantic express locomotives built by Baldwin between 1899 and 1901 and rated for speeds of 100 mph. They were Camelback locomotives with a square Wootten firebox measuring 96 by 96 inches.
Propulsion was provided by a Vauclain compound engine, i.e. with high and low pressure cylinders one above the other. A rebuild began as early as 1904, in which the four cylinders were replaced by two cylinders with simple expansion. One also increased the distance between the tube sheets by six inches to increase the heating surface area.