USAC's stock car division ran through the 1950s and into the 1970s. I'm not sure exactly when it started or ended. USAC, which stands for United States Auto Club, was the archenemy of NASCAR back in the 50s and 60s, and was also it's biggest competitor. When driver were banned, or just fueding by/with Bill France, USAC was usually where they went. USAC also sanctioned the Indianapolis 500 and was more into open wheel than stock cars.