Physics Hall at Iowa State University was constructed in 1923. In 1939, physics professor John Vincent Atanasoff, with the assistance of his graduate assistant Clifford Berry, built the prototype computer known as the ABC in the basement of Physics Hall. It was not until a lengthy court battle in 1973, however, that the ABC was officially recognized as the first electronic digital computer over the competing claims of Drs. John Mauchley and J. Prosper Eckert, the developers of the ENIAC. Currently, this building is used by the Department of Physics and Astronomy. The model was completed by Xin Li.