Cupples II is the oldest of the engineering buildings — its cornerstone was laid in 1901. It was one of the buildings given to the University by Samuel Cupples, and the first building to be built outside the original Quadrangle. The building was leased to the Louisiana Purchase Exposition Company during the 1904 World's Fair as the Jefferson Guard Building. In 1968 the north wall on the west half of the building was taken out so that a bridge could be built from Cupples II to the new engineering building, Bryan Hall.
Born on September 13, 1831, Samuel Cupples was a St. Louis woodenware merchant and business partner of Robert S. Brookings. With the Brookings Brothers, Cupples grew his company to enormous proportions. He also built "Cupples Station" in downtown St. Louis to aid in the transport of goods from the river to the railroad; the station became a most valuable asset to St. Louis merchants. In 1900, Cupples, with the agreement of Brookings, turned all company assets totaling $4 million over to the University in addition to funds for the construction of three new buildings: this building Cupples II, Cupples I Hall, and the Cupples Engineering Building, which was torn down in 1967 to make room for Bryan Hall. Cupples also served on the board of directors at Washington University.