Which Amendment made certain rights from the Bill of Rights applicable to the states?

The 14th Amendment is significant because it contains the Due Process Clause and the Equal Protection Clause, which have been interpreted by the courts to extend certain protections and rights enumerated in the Bill of Rights to the states. This process is known as "incorporation." Prior to the 14th Amendment, the Bill of Rights initially applied only to the federal government; however, through various Supreme Court decisions, many of these rights have been applied to the states, ensuring that state governments also uphold the fundamental rights of individuals. This amendment fundamentally altered the relationship between the states and the citizens' rights, promoting uniformity in legal protections across the country.

The other amendments mentioned do not have the same effect on the applicability of the Bill of Rights to the states. The 10th Amendment reserves powers not delegated to the federal government to the states or the people. The 12th Amendment addresses the electoral process for the president and vice president, and the 18th Amendment established the prohibition of alcohol, none of which pertains to the incorporation of rights from the Bill of Rights at the state level.