1. 1598 - On September 12, Spanish explorer Don Juan de Oñate led a group of settlers, including soldiers and families, across the Rio Grande near present-day San Elizario, Texas, and established the first European settlement in what is now New Mexico.

2. 1823 - September 12 marked the inauguration of New Mexico's first governor, Don Francisco Sarracino, under New Spain. Sarracino was a respected leader and worked to establish a stable civilian government in the territories.

3. 1846 - During the Mexican-American War, the Battle of Santa Cruz de la Cañada took place on September 12. This battle was fought between New Mexican militiamen and U.S. Army troops led by General Stephen Watts Kearny. Although the U.S. forces were victorious, the battle led to increased animosity between New Mexicans and Americans.

4. 1912 - On September 12 of this year, New Mexico officially became a state, joining the Union as the 47th state. The state's unique blend of Native American, Spanish, and Anglo-American cultures has contributed to its rich history.

5. 1947 - At the Roswell Army Air Field in Roswell, New Mexico, on September 12, an unusual object was recovered by military personnel, sparking rumors of a crashed UFO. The Roswell Incident remains a source of controversy and speculation to this day, and has become a part of New Mexico's popular culture.