Mario Andretti won a 30 lap USAC Sprint Car feature on the 1/2 mile dirt Cumberland Speedway in July of 1966. I've read (On the Internet) this was the first race USAC required cages on the sprints. I've also been told that USAC didn't require then until 1970.

Could this have instead been the first race a sprint car was entered in a USAC race with a cage? Thanks!

BTW USAC Eastern Sprints will be at Greater Cumberland Raceway Saturday April 11th 2020!