USS Illinois, built at Newport News, Virginia, was the name ship of a class of three 11,565-ton battleships. She was commissioned in September 1901. One of her first assignments was to test the newly-constructed floating dry dock at the Naval Station at New Orleans, Louisiana. In April and May 1902 she steamed across the Atlantic to visit European ports, but had to be repaired in England after accidently grounding at Christiana (Oslo), Norway, on 14 July. Illinois then resumed her European Squadron duties, including a tour in the Mediterranean Sea, before returning to the United States early in 1903. Thereafter she participated in regular fleet operations in the Western Atlantic and the Caribbean area.
In December 1907 Illinois steamed out of Hampton Roads, Virginia, to begin a voyage around South America. This was the first leg of the World Cruise of the "Great White Fleet". In company with most of the U.S. Navy's battleships, she arrived at California in the spring of 1908 and that summer crossed the Pacific to Australia and Asia. During the rest of 1908 and the first weeks of 1909 she transited the Indian Ocean, Suez Canal, Mediterranean Sea and the Atlantic, arriving back at Hampton Roads in February 1909. Some months later Illinois was decommissioned and underwent a major modernization, receiving new "cage" masts and more modern equipment.
After over two years in the shipyard and in reserve, Illinois returned to active service in 1912. During 1913 and 1914 she again went to Europe on training cruises and, after the United States entered World War I in April 1917, was employed for training along the East Coast. Illinois was placed in reserve at Philadelphia, Pennsylvania, in 1919. Given the hull number BB-7 in July 1920, the next year she became a training ship for the New York State Naval Militia and in 1922 was reduced to "unclassified" status. Subsequently disarmed and housed over as a floating armory, Illinoiscontinued in Naval Reserve service through the 1920s and 1930s. In January 1941 she was renamed Prairie State (IX-15). The old ship served through World War II as a Midshipmen's training school at New York and was kept there after the war to provide quarters for the Naval Reserve. USS Prairie State was stricken from the Navy list in March 1956 and sold for scrapping a few months later.