The triathlon began at 7am with a 1.2-mile swim followed by a 56-mile bike course along the gulf and a 13.1-mile run through Moody Gardens.
An award ceremony was held at 4pm.
Tim O'Donnell and Kelly Williamson, both of the USA, took first place for the men and women. O'Donnell crossed the finish line in 3:47:40 and Williamson's time was 4:13:27.
Favorable swim conditions kept competitors close, but Michael Raelert (DEU) emerged first from the water with a 1-second lead. O'Donnell made his first move of the day as he exited T1, followed by Raelert and Csaba Kuttor (HUN).
Cycling on a relatively flat bike course that went out and back along the Galveston Gulf Coast, O'Donnell saw his lead diminish as a number of competitors challenged for top position. Lance Armstrong (USA) surged away from the rest of his competitors just before the turnaround and held onto his lead into T2.
Ultimately, it came down to O'Donnell, who began the run in fourth place, overtaking Sebastian Kienle (DEU) and capturing his first win at the U.S Professional Championship.
The professional women saw strong swim performances with Anna Cleaver (NZL) exiting the water first with veteran Nina Kraft (DEU) close behind.
Cleaver held the lead early into the bike course until approximately the 10-mile mark, when Williamson -- the recently-crowned Ironman 70.3 San Juan champion -- made her move to the front. Amy Marsh (USA) and Anja Beranek (DEU) both made strong moves and entered T2 just seconds apart.
Beranek led in the beginning of the run course, but was quickly overtaken by Williamson, who captured her second Ironman 70.3 title in less than a month.
The finish line officially closed at 5:05pm. The event offers a total prize purse of $65,000 and 30 coveted slots to the 2012 Ironman World Championship 70.3, taking place September 9 at Lake Las Vegas.