Before the Territory was organized
Proposed boundaries for the earlier federal State of New Mexico, 1850
In 1846, during the Mexican–American War, the U.S. provisional government of New Mexico was established. Territorial boundaries were somewhat ambiguous. After the Mexican Republic formally ceded the region to the U.S.A. in 1848, this temporary wartime/military government persisted until September 9, 1850.
Earlier in the year 1850, a bid for New Mexico statehood was underway under a proposed state constitution prohibiting slavery. The request was approved at the same time that the Utah Territory was created to the north. The proposed state boundaries were to extend as far east as the 100th meridian West and as far north as the Arkansas River, thus encompassing the present-day Texas and Oklahoma panhandles and parts of present-day Kansas, Colorado, Utah, and Arizona, as well as most of present-day New Mexico. Texas raised great opposition to this plan, as it claimed much of the same territory, although it did not control these lands. In addition, slaveholders worried about not being able to expand slavery to the west of their current slave states.