Some little known facts about the 500:
1917-1918: Race is not held on account of World War I. Other tracks continue to host smaller events, but Indianapolis voluntarily suspends the race. Though closed to racing, the Speedway is used as an airstrip, serving as a fuel stop between Air Force bases in Dayton, Ohio and Rantoul, Illinois. (funny considering today we can go from Dayton, OH...around the world....back to Dayton without landing for fuel)
1942-1945: Race is not held due to World War II. The 1942 race was originally scheduled, but was cancelled in the days following Pearl Harbor. Unlike during WWI, all automobile racing is banned in the United States, primarily due to rationing. The Speedway gates were locked, and the facility was abandoned, left in a state of disrepair.