From 1924 to 1927 Indy cars raced on a 1.25 mile board track in Pineville, NC. According to one source, the track was made of green 2×4 lumber so that the boards would shrink allowing ventilation so the tires wouldn’t burn up during the race. On August 23, 1926, four races were held all sanctioned by the AAA. Two 25 mile Heats were followed by a 50 mile Semi and then a 150 mile feature race.
A notation on the back of the above postcard “1927 Indy cars ran on plank track”
So even back then they were known as “Indy Cars”
Earl Cooper and Dave Lewis won the heat races
Then the defending Indianapolis 500 winner Frank Lockhart would sweep the semi and feature
Frank would ave 120.878 MPH in his Miller for the victory