Residential burglary in the United States has declined by over 80% across the last four decades, representing a major social phenomenon that remains largely unexplained. International research indicates a need for investigation of the security hypothesis. Here, 50 years of studies are examined chronologically. A consistent narrative emerges which indicates that household security, largely absent in the 1970s, improved gradually over time. Improvement occurred via several mechanisms: the increased prevalence, quality, coverage, and routine use of security fixtures and fittings. In addition, crime displacement declined over time as fewer households offered easy crime opportunities, and the average age of burglars increased as juveniles found burglary increasingly difficult. Hence the study concludes that gradual household security improvements played a central role in the decline in residential burglary. While the findings suggest a considerable revison is needed to our understanding of burglary and burglars, the likelihood that 50 years of diverse burglary research points in the same direction by chance, and without significant contrary evidence, seems remote. Further implications for theory, policy, and research are identified.