Yea, we've seen a lot of growth, ever since ~2005. To show you how we got beat in skyline, we also need to account for population.
It was only when we had a population boom that our skyline went up with it to. And now we are the 6th fastest growing city in the USA.
In the 1970's:
Austin: 251,808
El Paso: 339,615 -Even they beat us in pop.
Fort Worth: 393,476 -Only until Austin had the upper hand when F.W dropped pop.
To the topic at hand:
Amarillo: On the Amarillo page on Wikipedia

Austin:
By Kevin Lehnhardt AKA KevinFromTexas