Millions of individuals and families in the United States do not have access to stable housing. Recent policies in the United States emphasize programs intended to prevent homelessness through temporary financial assistance. This paper explores the impact of the largest homelessness prevention program in U.S. history, the Homelessness Prevention and Rapid Rehousing Program (HPRP), on residential instability, using a national sample of families at risk of being homeless. Our identification strategy exploits variations on the location of HPRP providers, and the availability of funds. Using data on the proportion of K-12 students experiencing homelessness in school districts, we find that HPRP is associated with reductions in the percentage of homeless students for districts closer to an HPRP provider. Similarly, using the National Longitudinal Survey of Youth 1997, we find that HPRP reduced the probability of moving for families and individuals living in places where funding lasted longer. Our lower bound estimates show that the program prevented at least 210,000 to 300,000 individuals from entering to shelters, doubling-up, or living in places not meant for human habitation. This is equivalent to $3.8 to $5.3 billion saved in averted public assistance expenditures.