The highways numbered 81 and 90 that cross near the center of the map are pre-Interstate highways. The highways numbered 81 and 90 that cross near the center of the map are the Meridian Highway and the Old Spanish Trail, respectively.
They were part of the original United States Numbered Highway System, which was established in 1926. US 81 was originally designated as the Meridian Highway, and it ran from Winnipeg, Manitoba, Canada, to the Gulf of Mexico near Laredo, Texas. US 90 was originally designated as the Old Spanish Trail, and it ran from Jacksonville, Florida, to Los Angeles, California.
So, US 81 was replaced by Interstate 35 in Texas, and US 90 was replaced by Interstate 10 in Texas.