I found that out when I was getting into HDTV in the late 90s. The top 10 metro areas were required to be on the air first and that included Dallas/Fort-Worth(number 10), but not Houston(number 11). As of 2000, Houston's #10 while Dallas moved up to number 9.

[link|http://geography.about.com/library/weekly/aa010102a.htm|Largest Metrpolitan Areas]
Rank\tMetropolitan Area Name\t   States\t2000 Pop.\n 9\tDallas-Fort Worth\t   Texas\t5,221,801\n10\tHouston-Galveston-Brazoria Texas\t4,669,571