In the wake of United States v. Booker and Gall/Kimbrough v. United States, sentencing researchers and legal scholars conducted research designed to identify their impact on the federal sentencing process, with a focus on determining whether the decisions increased unwarranted disparity. In this article, we extend this body of research. Using 10 years of data from the U.S. Sentencing Commission and data from other sources, we assess whether and how these decisions influence sentence severity. Results indicate that sentence severity declined following Booker and, especially, Gall/Kimbrough, but that the decisions’ effects on sentence severity varied significantly across U.S. District Courts. Most importantly, the impact of Gall/Kimbrough sentence severity was conditioned by districts’ percent Black population, level of socioeconomic disadvantage, and degree of political conservatism; each of these factors moderated the decisions’ effects on the harshness of the sentences imposed by the districts’ judges.