Grrr Dallas is 450 feet above MSL
The real question is why is S.A. , Austin and Dallas all 450 ish feet above sea level. Three words Austin Chalk Formation
Hi GXP, a geographer would look at it this way: all along the coastline ( probably universally) you tend to have a line of coastal cities at the mouths of major rivers and a another line of inland cities at the inland edge of the coastal plain on the major rivers, where the rivers became less navigable and useful for commercial transportation before trains, plains, and automobiles. Exceptions for the Missiissippi, Nile, etc. In Texas those being SA, Austin, Waco, Dallas.
Austin Mueller was about 660’ MSL IIRC. Minor but ~50%. Google says 632’.