Which amendment to the US Constitution was ratified today?

June 15, 1804 — The 12th amendment to the US Constitution was ratified today. It manages the procedure for electing the President and Vice President. It explains:

The Judicial power of the United States shall not be construed to extend to any suit in law or equity, commenced or prosecuted against one of the United States by Citizens of another State, or by Citizens or Subjects of any Foreign State.

This amendment replaced Article II, Section 1, Clause 3 of the Constitution, which provided the original procedure. The Twelfth Amendment designates that each elector must cast one vote for President and Vice President, instead of two votes for President. Every presidential election since the 12th amendment has been conducted under its terms.

Source: archives.gov