(Friday, October 16, 1846, just after midnight local time) — Dentist William T. G. Morton demonstrated the effectiveness of ether as an anesthetic today by administering it to a patient undergoing jaw surgery before an audience of doctors at the operating theater of the Massachusetts General Hospital, or MGH.
(Thursday, September 24, 1846, just after midnight local time) — Neptune, the eighth and farthest known planet from the Sun in the Solar System, was identified as a planet early this morning at the Berlin Observatory by German astronomer Johann Gottfried Galle.
(Thursday, August 18, 1846; during the Mexican-American War) — U.S. forces led by Gen. Stephen W. Kearny occupied Santa Fe today in present-day New Mexico, bringing nearly two and a half centuries of Spanish and Mexican rule to an end without firing a shot.
Video: 'Mexican American War - 2of6' (Congress approves declaration of war at :21)
(Wednesday, May 13, 1846; during the Mexican-American War) — The U.S. Congress approved a declaration of war on Mexico requested by President James Polk today after a few hours of debate on a vote of 40-2 in the Senate and 174-14 in the House.
Video: 'Mexican American War - 2of6' (Battle of Palo Alto at 1:33)
(Friday, May 8, 1846, 2:00 p.m. local time; during the Mexican-American War) — The first major battle of the Mexican-American War was fought today at Palo Alto, Texas; U.S. forces led by Gen. Zachary Taylor were able to beat back Mexican forces.