If current climate change trends continue, flooding, extreme heat, wildfires, and water scarcity will make the homes of millions of people in the United States increasingly uninhabitable. This change could happen by the end of the century, perhaps sooner. Most people will want to stay in their current homes, but there is no coherent policy to fortify the most vulnerable places. Nor is the current legal system equipped to handle what may become one of the largest migrations in U.S. history, as people flee intolerable climate conditions. This Article envisions five scenarios for cities in the future: sprout, grow, stay, shrink, or leave. It argues that every city, and perhaps each neighborhood, will need to decide which scenario to follow and analyzes the legal implications of each.