Isn't Knoxville, Iowa west of the Mississippi River?
"USAC Sprints Return to Knoxville on June 3, 2017
Get ready! The USAC AMSOIL Sprint Car National Championship returns to the legendary half-mile Knoxville Raceway in Iowa on June 3, 2017 for National Sprint Car Hall of Fame Weekend! #nowings"
https://twitter.com/USACNation