This paper seeks to explain three key components of the growing regional disparities in the U.S. since 1980, referred to as the Great Divergence by Moretti (2012). Namely, big cities saw a larger increase in the relative wages of skilled workers, a larger increase in the relative supply of skilled workers, and a smaller decline in business dynamism. These trends can be explained by differences across cities in the extent to which firms adopt new skill-biased technologies. In response to the introduction of a new skill-biased, high fixed cost but low marginal cost technology, firms endogenously adopt more in big cities, in cities that offer abundant amenities for high-skilled workers and in cities that are more productive in using high-skilled labor. The differences in adoption can account for the increasing relationship between skill intensity and city size, the divergence of the city size wage premium by skill group and the changing cross sectional patterns of business dynamism. I document a new fact that firms in big cities invest more in Information and Communication Technology per employee than firms in small cities,consistent with patterns of technology adoption in the model.