1. On December 15, 1846, the Battle of Rio San Gabriel took place in Los Angeles, California, during the Mexican-American War. Many New Mexicans, including Governor Manuel Armijo, served in the Mexican army during the conflict.

2. In 1880, New Mexico's first official weather record was taken on December 15. The temperature in Santa Fe was recorded at -13 degrees Fahrenheit, the lowest ever recorded in the city.

3. December 15, 1891, marked the opening of the New Mexico Normal School (now Eastern New Mexico University) in Portales. The institution was created to prepare teachers for the rapidly growing population of New Mexico.

4. In 1924, New Mexico became the 47th state to ratify the 19th Amendment to the U.S. Constitution, which granted women the right to vote. The state's ratification came on December 15, just over four years after the amendment was adopted by Congress.

5. On December 15, 1947, the United States Air Force announced the completion of the "X-1" rocket plane, which was designed to break the sound barrier. The plane was flown by Captain Charles "Chuck" Yeager, who became the first person to break the sound barrier on October 14, 1947, over the deserts of New Mexico.