This dissertation examines the wave of seventeen historic district designations that took place from 2007 through 2015 in Brooklyn, New York, following a ten-year period that lacked any. Its core question is can historic districting in the 21st century help communities preserve their social fabric, at the same time as their architectural, and if so, how? First, through a literature review, the Introduction establishes that the field of Historic Preservation has become increasingly socially conscious over the last few decades, developing goals, backed by theory, to continuously expand its base of constituents. Then, the dissertation proceeds in three methodologically defined chapters. Testing whether the social goals of Preservation are reflected in the recent wave of designations, the first chapter develops and applies a Census data methodology to the historic districts of Brooklyn, creating two subsets based on year of designation, and finds that the newly-designated districts exhibit characteristics that strongly confirm increasing social inclusivity and diversity. Next, eight months of fieldwork research in a newly-designated area reveal how the processes embodied in the Landmarks Law, though nominally pertinent to the built environment alone, are being channeled to protect the social fabric of community. This chapter ultimately argues, therefore, that historic districting in 21st century Brooklyn can be understood as a method of “self-preservation.” The third chapter, using developments in Open data and Civic technology, analyzes three other related trends. It reveals that changes in rent-stabilized housing, property turnover, and the growing presence of LLCs in real estate are complicating whether the Preservation community can realize its goals. This dissertation aims to make substantive and methodological contributions to a deeper understanding of 21st century Preservation. The new wave of designations is characterized by greater inclusivity and diversity, and communities are channeling Preservation processes and regulations toward protecting their social fabric, but larger forces compete. In exploring these dimensions of 21st century Preservation, a refined approach to Census data analysis, community-engaged research, and Open data and Civic tech methods are applied and discussed. Ideally, both the information and the methods prove germane and useful for future research.