Background Preventing child falls from windows is easily accomplished by installing inexpensive window-limiting devices but window falls remain a common cause of child injuries. This article describes the history and evolution of the New York City (NYC) window guard rule,which requires building owners to install window guards in apartments housing children aged ≤10 years. The NYC window guard rule was the first directive of its kind in the USA when it was adopted in 1976, and it has led to a dramatic and long-lasting reduction in child window fall-related injuries and deaths.

Methods Data about the history of the window guard rule were obtained by reviewing programmatic records, correspondence, legal decisions and the published literature. In addition, key informant interviews were conducted with programme staff.

Results and Discussion This article describes each stage of policy development, starting with epidemiological studies defining the scope of the problem in the 1960s and pilot-testing of the window guard intervention. We describe the adoption, implementation and enforcement of the rule. In addition, we show how the rule was modified over time and document the rule’s impact on window fall incidence in NYC. We describe litigation that challenged the rule’s constitutionality and discuss the legal arguments used by opponents of the rule. Finally, we discuss criminal and tort liability as drivers of compliance and summarise lessons learnt.