In the United States, preemption is a legal doctrine that allows upper levels of government to restrict or even prevent a lower-level government from self-regulating. While it is often thought of in the context of the federal government preventing state regulation, preemption is increasingly used as a tool by states to limit cities, counties, and other lower-level municipalities from legislating across a broad array of issues.  This map identifies key features of state-level preemption laws in 50 states, from August 1, 2019, to November 1, 2021.