In this article, we take a fresh look at the geographical determinants of innovation, doing so by examining density, and more specifically the density of creativity, as a key factor influencing metropolitan area innovation. Density has become a topic of increasing interest to scholars studying the factors that influence regional innovation and growth. This article builds upon this recent attention while also extending the existing literature on the determinants of regional innovation in a number of important ways, foremost by focusing on the relationship between innovation outcomes and the interaction of highly skilled individuals and population density. In doing so, we expand upon, and in some important ways depart from, the inter-related concepts of proximity, knowledge spillovers, and face-to-face interactions of intellectual human capital often discussed in recent economic geography literature. A few recent papers have begun to explore the relationship between forms of density and the production of new knowledge. For example, at the state level, Ciccone and Hall (1996) find that employment density increases average labor productivity, while Sedgely and Elmslie (2004) find a positive relationship between state population density and innovation.