The stateless population is difficult to identify in US government data and, more broadly, in US society in part because no government entity makes statelessness determinations or systematically collects information on stateless populations. Few (if any) federal immigration officials that encounter stateless persons are trained or tasked to identify them. Failing to look for stateless persons, federal, state and local governments fail to find them. The lack of a designated path for stateless persons to register or to secure legal status, in turn, makes stateless persons less likely to disclose their status and increases their sense of isolation. In order to attempt to map statelessness in the United States, CMS developed a methodology that accounted for these factors. It incorporates quantitative and qualitative research approaches to attempt to estimate the size of the population of potentially stateless persons or those potentially at risk of statelessness in the United States, to profile distinct populations, and to document their situations, challenges and lived experiences. After conducting preliminary research, CMS convened a group of 28 statelessness experts in October 2017 to discuss the sources, strengths, and limitations of data on statelessness, to identify particular concentrations of stateless persons, and to examine CMS’s proposed methodology. The group included government officials, statisticians, analysts, scholars, human rights experts, legal professionals, and stateless persons. In preparation for the meeting, CMS produced a literature review that included UNHCR mapping statelessness studies for other countries, academic articles, and policy reports. Prior to this study, the stateless population in the United States was unofficially estimated to be around 4,000 persons (UNHCR 2015a, 9), a figure extrapolated from the number of stateless asylum seekers over a 10-year period. As a way to focus the discussion, CMS provided its draft profiles of populations in the United States that are potentially stateless or potentially at risk of statelessness to its project advisors, who fine-tuned profile descriptions and identified additional populations to include. To ensure that the research met the highest ethical standards, CMS sought a full board review of its qualitative methods—which included an online survey and in-depth interviews with stateless individuals— from Syracuse University’s Institutional Review Board (IRB). As part of the IRB application process, interviewers completed the relevant Collaborative Institutional Training Initiative (CITI) Web-based training program for human subjects, as required by Syracuse University. CMS submitted the interview protocol, survey, informed consent form, phone and email scripts, and outreach materials to the IRB as part of its application. Following the expert advisory group meeting, CMS developed an online survey (Attachment A) for community-based organizations (CBOs), legal service providers, ethnic organizations, faithbased entities, and other non-governmental organizations (NGOs) that may represent, serve or otherwise encounter stateless persons. The survey had four overarching purposes: (1) to identify stateless persons to interview; (2) to supplement CMS’s stateless profiles; (3) to develop a fuller understanding of the causes and challenges of statelessness; and (4) to expand the growing network of service providers and stateless persons who could educate the public on this issue. The survey asked non-identifying details about stateless individuals, such as the causes of their 6