The construction of the Illinois National Guard Armory, 605 N. Main Street, began in 1934 with the selection of a site and architect Bradley & Bradley for the project. With the completed Art Deco style plans, Sjostrom & Sons, Inc. was contracted for the construction. The project began in 1936 and was dedicated in 1937. Throughout WWII and on into the Cold War the Illinois National Guard occupied the facility.
The building was placed on the National Register of Historic Places on August 10, 2000.
Benson Stone created unique stonework for the building's facade.
In 1991, a new armory was built north of Machesney Park. The contract was awarded to Robert R. Stenstrom, Inc. The complex occupied 10.15 acres and contains over 50,000 square feet.