Possible Clues:

• Astros' MLB division
• Division with A's
• Mariners' div
• Brewers once worked there
• MLB division with CA teams
• Texas Rangers' div
• M.L.B. division that includes the Astros
• The 'Stros joined it in 2013
• Home to every M.L.B. club whose name starts with 'A'
• L.A. Angels' division