1. The Treaty of Guadalupe Hidalgo was signed on March 21, 1848, bringing an end to the Mexican-American War and officially ceding New Mexico to the United States.

2. On March 21, 1876, the first train arrived in the town of Las Vegas, New Mexico, marking the dawn of a new era for transportation and commerce in the state.

3. In 1904, the New Mexico School for the Deaf was established in Santa Fe on March 21, providing educational opportunities for deaf and hard-of-hearing students in the region.

4. March 21, 1922, marked the founding of the University of New Mexico Press, which has since become one of the leading publishers of scholarly books on the history, culture, and natural resources of the Southwest.

5. On March 21, 1945, the first atomic bomb test was conducted at the Trinity Site in southern New Mexico, a pivotal moment in the development of nuclear weapons that would have profound implications for the state, the nation, and the world.