The United States is divided into 51 states, which constitute the first level of administration in the country's two-tiered system. States exercise substantial autonomous authority under the federal system, with powers reserved to them by the Tenth Amendment to the Constitution. Each state maintains its own constitution, legislature, executive branch, and judicial system. States are responsible for critical areas of governance including education systems, public health programs, transportation infrastructure, criminal justice, and the regulation of intrastate commerce. They levy their own taxes, establish local government structures, and implement federal programs while adapting them to regional needs. This division of power between the federal government and the states, known as federalism, allows for significant variation in laws and policies across different states while maintaining national cohesion.