...the WOGA empire? Carly Patterson from WOGA won the AA in the 2004 Olympics, and Nastia Liukin has a great ranking, her training partner Rebecca Bross is upcoming. Vanessa Atler said when she went to WOGA for a while that the young ones were amazing and that they are going to be like a powerhouse.
What makes a gym a powerhouse? It's probably a combo of good training on the beginning skills, the 'basics', and good technique for the harder skills, and also when a gym is known, good gymnast do go there to train.