[2] It was created from the U.S. provisional government of New Mexico, as a result of Nuevo México becoming part of the American frontier after the Treaty of Guadalupe Hidalgo.

After the Mexican Republic formally ceded the region to the United States in 1848, this temporary wartime/military government operated until September 9, 1850.

Others, including Abraham Lincoln, insisted that older Mexican Republic legal traditions of the territory, which abolished black slavery in 1834, took precedence and should be continued.

[5] As one of the final attempts at compromise to avoid the Civil War, in December 1860, a U.S. House of Representatives committee proposed to admit New Mexico as a slave state immediately.

As in New Mexico, slavery was already extremely limited, due to earlier Mexican traditions, laws, and patterns of settlement.

The new border included a few miles of the Colorado River at the western end; the remaining land portion consisted of line segments between points, including 32°29′38″N 114°48′47″W / 32.49399°N 114.813043°W / 32.49399; -114.813043 at the Colorado River, west of Nogales at 31°19′56″N 111°04′27″W / 31.33214°N 111.07423°W / 31.33214; -111.07423, near AZ-NM-Mexico tripoint at 31°19′56″N 109°03′02″W / 31.332099°N 109.05047°W / 31.332099; -109.05047, the eastern corners of NM southern bootheel (Hidalgo County) at 31°47′02″N 108°12′31″W / 31.78378°N 108.20854°W / 31.78378; -108.20854, and the west bank of Rio Grande at 31°47′02″N 106°31′43″W / 31.78377°N 106.52864°W / 31.78377; -106.52864.

Although this area was smaller than what had been included in the failed statehood proposal of early 1850, the boundary disputes with Texas had been dispelled by the Compromise of 1850.

The Battle of Glorieta Pass in May 1862, following the retreat of Texan Confederate forces back south to El Paso, placed the area of the Rio Grande valley and eastern New Mexico Territory with the capital of Santa Fe under the control of the Federals with their Union Army.

[10] However, the government and leadership of Confederate Arizona persisted until the end of the Civil War in June 1865 with the surrender of the Trans-Mississippi Department, living in exile in El Paso, Texas with its delegate still in Richmond.

[11][12] The legislation, titled "An Act adopting and establishing the coat of arms and great seal of the territory", was approved by Governor Edmund G. Ross on February 1:[11] The coat of arms of the territory of New Mexico shall be the Mexican Eagle grasping a serpent in its beak, the cactus in its talons, shielded by the American eagle with outspread wings, and grasping arrows in its talons.