A growing body of research has been documenting the pivotal role that philanthropic funding plays in advancing state and local charter school reform. However, there is little understanding of the geographic flow of these funding patterns and the market, policy, and organizational conditions that have concentrated funding in some clusters of states more than others. To address this limitation, we use descriptive cartography and quadratic assignment procedure (QAP) regression to analyze longitudinal funding data from 15 philanthropic foundations along with data related to the contexts of the states where grant recipients reside. We find that between 2009 and 2014, foundations were increasingly converging their funding flows to charter school organizations in select clusters of states as they shifted the concentration of funds away from individual charter schools to charter management organizations (CMOs) and advocacy organizations. A substantial portion of the variation in this interstate convergent grant funding was associated with previously established funding flows. However, the local market and policy contexts of states and certain forms of evidence of charter school effectiveness were also associated with interstate convergent funding. These findings point to the potential ways public policy and research can shape the flow of private money into public education and yet illuminate substantial geographic inequality in the ways these funds are distributed.