1846 – U.S. annexation of California was proclaimed at Monterey after the surrender of a Mexican garrison.
1865 – Four people were hanged in Washington, D.C., after being convicted of conspiring with John Wilkes Booth to assassinate President Abraham Lincoln.
1898 – The United States annexed Hawaii.
1930 – Construction began on Boulder Dam on the Colorado River.
1981 – President Ronald Reagan announced he was nominating Sandra Day O’Connor to become the first female justice on the U.S. Supreme Court.
1987 – Lt. Col. Oliver North began his public testimony at the Iran-Contra hearing, telling Congress that he had “never carried out a single act, not one” without authorization.