In January 1948, the University of Illinois' Board of Trustees appropriated $150,000 for the construction of a computer by New York's Reeves Instrument Company.
As it became clear that the company could not deliver the computer on time, John von Neumann of the Institute for Advanced Study (IAS) at Princeton University suggested that the University of Illinois construct its own computer, which would become ILLIAC I.
The Board of Trustees canceled the contract with Reeves and obtained permission from J. Robert Oppenheimer, the Director of IAS, to build a computer based upon von Neumann's design at llinois. Physicist Ralph Meagher was appointed chief engineer.
At the same time, the University obtained from the U.S. Army an order for an identical computer for the Aberdeen Proving Ground in Maryland. This machine, the ORDVAC, was the first of the two computers completed, passing its acceptance tests in February of 1952. ILLIAC I, the University's computer, went online on September 22, 1952. Originally, it was available for use only eight hours a day.
The ILLIAC I used 2,800 vacuum tubes, and measured ten feet high, two feet wide, and eight and a half feet tall. The total weight of the machine was five tons. It would stay in service for ten years, providing computing power for the entire University, finding use in the design of other research instruments such as high-energy particle accelerators and the University's radio telescope.