Historic tax credit (HTC) programs and similar financial incentives have historically filled a critical financing gap in the rehabilitation of historic buildings, effectively providing capital to projects that otherwise would not be economically feasible and generating development in small or economically disadvantaged communities. Specifically, state HTC programs parallel to the federal historic tax credit program leverage additional private and local investment and encourage the stewardship and rehabilitation of historic buildings. State HTC programs also generate several benefits throughout local communities, including the creation and preservation of affordable housing units. As cities seek out ways to mitigate a growing number of affordable housing problems and reinvest in their historic built environment, financial incentives at the state level figure to have an important, if not critical, role. Therefore, this thesis cross-analyzes all state historic tax credit programs throughout the United States to determine the most effective attributes for generating rehabilitation projects with affordable housing outcomes. This thesis identifies how state programs can catalyze affordable housing through the historic built environment by way of a comparative analysis of the regulatory structure of state HTC programs and a qualitative synthesis of program data from recent fiscal years. The analysis relies on a national survey of existing enabling legislation across each state, HTC coordinator communication, and case studies to determine the enabling and constraining attributes of state HTC programs as determinants of affordable housing rehabilitations and preservation.