After spending a half-century in the National League, the Astros switched to the AL West this year to give baseball an even 15 teams in both leagues.
The change is a fresh start for the Astros, who are coming off consecutive 100-loss seasons but are hoping to redefine the franchise with a new manager, Bo Porter, and new uniforms.
In front of an excited home Houston crowd at Minute Maid Park, the Astros made the most of their moment in the spotlight as they got their season underway a day ahead of the majority of teams.
Starter Bud Norris tossed 5 2/3 solid innings while the offense came alive behind him.
Justin Maxwell opened the scoring with a two-run triple in the fourth inning and the Astros added two more runs in the fifth before Texas cut the lead to 4-2 in the top of the sixth.
In the bottom of the sixth, however, pinch-hitter Rick Ankiel delivered the game's biggest blow, a three-run home run against reliever Derek Lowe that made it 7-2.
Lowe had just entered the game in relief of Matt Harrison, who suffered a tough start after his career-best 2012 season earned him a five-year extension with Texas.
The Rangers, too, unveiled a new-look roster without former MVP Josh Hamilton, catcher Mike Napoli and infielder Michael Young.