Each year in the United States, thousands of Americans die in motor vehicle crashes, incurring monumental human and economic cost on society. There has been much research in the past decades to understand the circumstances surrounding them. While previous research has looked at nationwide traffic statistics and compared crash rates between states, there is a dearth of literature on interstate and crashes within states, especially in temporal contexts. To answer research questions on fatal crashes, one usually uses the Fatality Analysis Reporting System (FARS) data, which are publicly available from the National Highway Traffic Safety Administration (NHTSA). However, the 42 years of FARS data are collected annually, with differing representations of concepts and data elements from year to year. To facilitate analysis of such long-term effects of changes to policy, vehicle characteristics, and roadway infrastructure, we created a single FARS data resource through recoding, harmonization, and integration of all 42 years of the Accident, Person, and Vehicle files that comprise FARS. In this poster we describe the process of building an ontology and using it to integrate these heterogeneous data. We also discuss assumptions that must be made when converting older data to modern coding schemas, as well as the limitations of our approach and the resulting dataset. We will use these data to investigate temporal trends of the effects of state- and regional-specific policy changes on road safety and crash characteristics with a goal of developing policy proposals to reduce future crashes.