FINALLY! Found it. The first Fair Park Stadium, built in 1921 (Courtesy Texas State Historical Society). It seated about 15,000 people and was wooden. The future Cotton Bowl, also named Fair Park Stadium for it's first six years, would be built right inside the horse track which is the curve just below FP stadium. In this photo, it's Texas versus Vanderbilt University at the first Fair Park Stadium on Oct. 20, 1923

1922 Sanborn Map. Pennsylvania Ave is the same road that is at the top of the photo above to give you orientation.

In this SMU Digital Collections aerial survey, you can blow it up to still see the FP Stadium toward the right where the #10 is. It still existed when the future Cotton Bowl was built. #10 is Pennsylvania Ave.
https://digitalcollections.smu.edu/digital/collection/dmp/id/163?fbclid=IwAR1ilYutTJBs4VVSWiZ8GJ1LBHOI37NSGz5-lOS3AFOaMXo1OXEwdc8pxfM
Built in 1930, the future Cotton Bowl is inside the old horse track. However it was not called Cotton Bowl for several more years. It was also called the Fair Park Stadium at that time. Not until the Cotton Bowl Classic was put together was the Stadium renamed the Cotton Bowl. First Classic was played Jan 1, 1937
Google Map of today. Go to Pennsylvania Ave to get your orientation
https://www.google.com/maps/place/Botanica+El+Amanecer/@32.7779017,-96.7579871,17z/data=!4m6!3m5!1s0x864e9a374c58aa99:0x366d370a9ea9ea87!8m2!3d32.7761318!4d-96.7508102!16s%2Fg%2F1tj96v35?entry=ttu

1922 Sanborn Map. Pennsylvania Ave is the same road that is at the top of the photo above to give you orientation.

In this SMU Digital Collections aerial survey, you can blow it up to still see the FP Stadium toward the right where the #10 is. It still existed when the future Cotton Bowl was built. #10 is Pennsylvania Ave.
https://digitalcollections.smu.edu/digital/collection/dmp/id/163?fbclid=IwAR1ilYutTJBs4VVSWiZ8GJ1LBHOI37NSGz5-lOS3AFOaMXo1OXEwdc8pxfM
Built in 1930, the future Cotton Bowl is inside the old horse track. However it was not called Cotton Bowl for several more years. It was also called the Fair Park Stadium at that time. Not until the Cotton Bowl Classic was put together was the Stadium renamed the Cotton Bowl. First Classic was played Jan 1, 1937
Google Map of today. Go to Pennsylvania Ave to get your orientation
https://www.google.com/maps/place/Botanica+El+Amanecer/@32.7779017,-96.7579871,17z/data=!4m6!3m5!1s0x864e9a374c58aa99:0x366d370a9ea9ea87!8m2!3d32.7761318!4d-96.7508102!16s%2Fg%2F1tj96v35?entry=ttu