Which amendment reserves powers not delegated to the national government to the states?

The 10th Amendment is crucial because it explicitly states that powers not delegated to the federal government by the Constitution, nor prohibited to the states, are reserved for the states or the people. This amendment was part of the Bill of Rights, ratified in 1791, and reflects the principle of federalism that underlies the American governmental structure. The intent behind the 10th Amendment is to ensure that states retain a significant amount of power and autonomy, allowing them to govern on issues not specifically outlined in the Constitution.

In contrast, the other amendments listed do not pertain to the distribution of power between the national government and the states. The 9th Amendment addresses the rights of the people that are not specifically enumerated in the Constitution, while the 11th Amendment deals with sovereign immunity, and the 12th Amendment outlines the procedure for electing the President and Vice President. These differences highlight the specific role the 10th Amendment plays in the context of state versus federal authority.