What geographic pull factors shape where individuals engage in startup activity? The related literatures discuss how agglomeration forces shape the geographic locus of innovation, characterize the business environment influencing individual mobility, and suggest that local spinoffs can lead to industry clustering. To improve our understanding of why some individuals move geographies (bypassing their home social capital) to start new ventures, we evaluate three candidates: venture capital access, specialized human capital access, and co-location to access knowledge spillovers. Using startups in the artificial intelligence (AI) industry, we examine the relative empirical importance of these factors in the 2001-2018 timeframe. We find that our measures of knowledge spillover capital and human capital best explain geographic pull factors for entrepreneurship, especially after a major technological advance.