It was built in 1898 and was designed by W. A. McGinnis in the Victorian Queen Anne style with Richardsonian Romanesque influences.

In his speech, he envisioned the opportunities the dam and the resulting irrigation for farming would create for Arizona and opined that some day perhaps as many as 100,000 people might live in the valley.

Thanks to a $5.7 million campaign led by the ASU Alumni Association, the building was refurbished to the period in which it was constructed.

[4] Old Main is a two and one-half stories tall brick 30-by-135-foot (9.1 m × 41.1 m) building with a full basement set on a granite base.

It has a hipped and projecting gabled pressed-metal roof with castellated cresting and metal ridge finials, and a red sandstone entrance stairway.