The combination of President William McKinley's assassination on September 14, 1901 and the threat of unfavorable weather conditions delayed the cornerstone laying until 1902.

[6] Overall construction is incomplete, with the interior unfinished, and was put on hold due to a lack of funds from American University.

Camp Leach with acres of barracks was created on campus and the McKinley building was to be turned over to the Bureau of Mines after completion of the interior, renovations which the government paid for.

The U.S. modified and finished the interior of McKinley Building, creating the chemical weapons lab, one of the biggest in the nation.

[9] The United States Department of Agriculture leased McKinley for the use of the Nitrate Division (which later became the Fixed Nitrogen Research Laboratory).

Renovation made way for The School of Business, The American Language Center, The District Speech Clinic, and The Education Department.

An exploration of the attic chronicled in an article in The Eagle published Nov. 15, 1966 revealed that a portion of the bare, unused space holds "a maze of telephone wires" and "a complex of electronic equipment.

An article in The Eagle written in September of 1967 quoting the AU Director of Physical Plant clarifies that the receivers are backup Federal Transmitters.