As e-commerce began making department stores passé, chains like Macy’s, J.C. Penney, and Sears tried to stop the bleeding by closing hundreds of locations. Wisconsin-based Kohl’s, in contrast, kept stores open while racing to upgrade its own technology. Today it’s recognized as one of retail’s savviest survivors—its stock has nearly doubled in the past year. Gass, a Starbucks veteran who helped make “frappuccino” a household word, has been CEO only since May. But during her five years at Kohl’s, she engineered many of its most successful innovations, including big bets on Under Armour and other activewear brands. Her latest experiment: a risky but revolutionary partnership with Amazon.