Which amendment is often associated with states' rights?

The Tenth Amendment is often associated with states' rights because it explicitly reserves to the states and the people any powers that are not delegated to the federal government by the Constitution. This amendment reflects the principle of federalism, where power is divided between the national and state governments. By emphasizing that states retain certain powers, the Tenth Amendment supports the idea that states have the authority to enact laws and policies that are specific to their needs and circumstances, as long as they do not conflict with federal laws.

In contrast, the other amendments mentioned do not focus on the distribution of power between state and federal governments. The First Amendment primarily protects individual freedoms, such as speech, religion, and assembly. The Fifteenth Amendment addresses voting rights and prohibits the government from denying a citizen's right to vote based on race, while the Twentieth Amendment deals with the terms of elected federal officials and does not pertain to states' rights. Thus, the Tenth Amendment stands out as the one directly connected to the concept of states' rights.