From its inception in 1911, the Indianapolis 500 has been considered the marquee event of Championship/Indy car racing. The race has been held every year from 1911, with the exception of 1917-1918 (World War I) and 1942-1945 (World War II). The Indianapolis 500 has been part of an official national championship in 1916, 1920–1941, and since 1946. In the years from 1911 to 1915, as well as 1919, the race was held as a formally sanctioned event, but an official national championship was not recognized in those years. Therefore, those six editions of the race were not attached to an officially recognized national championship.