What were the consequences of penal transportation to the New World for eighteenth-century British criminal justice? Transportation has been described by scholars as either a replacement of the death penalty responsible for its decline, or a penal innovation responsible for punishing a multitude of people more severely than they would have been punished before. Using data from the Old Bailey Sessions Papers and the Parliamentary Papers, this study examines sentencing and execution trends in eighteenth-century London. It takes advantage of the natural experiment provided by the passage of the 1718 Transportation Act that made transportation available as a penal sentence, thus enabling one to assess the “effect” of transportation on penal trends. This study finds that the primary consequence of the adoption of transportation was to make the criminal justice net more dense by subjecting people to a more intense punishment. While it was also associated with a small decline in capital sentences for some types of offenders, the adoption of transportation was also associated with an increase in the rate at which condemned inmates were executed. The study closes with a discussion of the conditions that may lead to law's unintended consequences, including the mesh-thinning consequences observed here.