From Twitter Motorsports

The United States Automobile Club (USAC) is an open-wheel auto racing sanctioning body. From 1956 to 1979, the USAC sanctioned the United States National Championship, and from 1956 to 1997 it sanctioned the Indianapolis 500. USAC is the sanctioning body for:

• USAC Silver Crown Series
• USAC Sprint Car Series
• USAC Mopar Midget Series
• USAC Ford Series
• USAC Quarter Midgets

[edit] USAC on Twitter

• @USAClive - Official series

USAC — United States Automobile Club

Silver Crown Series  |  Sprint Car Series  |  Mopar Midget Series  |  Ford Series  |  Quarter Midgets