Infantry Regiment of the Civil War, also known as the Fox Valley Regiment was organized in Aurora in September of 1861. According to the Adjutant General's Report, the Regiment included 965 officers and enlisted men, forty-seven being from DuPage County. Officers from Cook, Grundy, Kane, Kendall, Lawrence, McHenry and Warren Counties completed the regiment.

The 36th Illinois fought in many battles including Pea Ridge, Perryville, Stone River, Chickamauga, Mission Ridge, Resaca, Adairsville, Dallas, Kenesaw, Atlanta, Franklin and Nashville.

Made of painted silk, this flag was brought back to Springfield after the war. Recently professionally conserved with intensive cleaning and precise repair of the fabric, the restoration of the flag has ensured that it will be an educational tool for generations to come. The restoration was made possible by generous efforts of the Illinois State Military Museum, The Illinois National Guard, the DuPage County Historical Museum, Illinois Sons of Union Veterans of the Civil War Camps 1 and 2, The Civil War Roundtable of Chicago, The Salt Creek Civil War Roundtable, the McCormick Foundation and many individuals. On loan from the Illinois State Military Museum.