page_title: Southwestern United States
section_title: Becoming states
hierarchical_section_title: Southwestern United States / History / Becoming states
caption_attribution_description: Map of the states and territories of the United States as it was from 1850 to March 1853. On September 9 1850, several western areas changed: The Mexican Cession was organized, being split in to Utah Territory and New Mexico Territory, and one portion was admitted as the state of California. These two territories also included a portion of Texas, ceded to the federal government. Finally, a small area known as the Neutral Strip as not officially included in any state or territory. A small portion of Texas and the Mexican Cession became unorganized land. On March 2 1853, Washington Territory was split from Oregon Territory.
context_page_description: The Southwestern United States, also known as the American Southwest, Desert Southwest, or simply the Southwest, is the informal name for a region of the western United States. Definitions of the region's boundaries vary a great deal and have never been standardized, though many boundaries have been proposed. For example, one definition includes the stretch from the Mojave Desert in California to Carlsbad, New Mexico, and from the Mexico–United States border to the southern areas of Colorado, Utah, and Nevada. The largest metropolitan areas are centered around Phoenix, Las Vegas, Tucson, Albuquerque, and El Paso. Those five metropolitan areas have an estimated total population of more than 9.6 million as of 2017, with nearly 60 percent of them living in the two Arizona cities—Phoenix and Tucson.
  Most of the area was part of the Viceroyalty of New Spain in the Spanish Empire before becoming part of Mexico. European settlement was almost non-existent outside New Mexico in 1848, when it became part of the United States through the Treaty of Guadalupe Hidalgo, while southern areas of Arizona and southwestern New Mexico were added in the later Gadsden Purchase.
context_section_description: Of the states of which at least a portion make up the Southwest, Texas was the first to achieve statehood. On December 29, 1845 the Republic of Texas was annexed, bypassing the status of becoming a territory, and immediately became a state. Initially, its borders included parts of what would become several other states: almost half of New Mexico, a third of Colorado, and small portions of Kansas, Oklahoma, and Wyoming. Texas current borders were set in the Compromise of 1850, where Texas ceded land to the federal government in exchange for $10 million, which would go to paying off the debt Texas had accumulated in its war with Mexico.
  Following the Mexican Cession, the lands of what had been the Mexican territory of Alta California were in flux: portions of what is now New Mexico were claimed, but never controlled, by Texas. With the Compromise of 1850, the states of Texas and California were created (Texas as a slave state, and California as a free state), as well as the Utah Territory and New Mexico Territory. The New Mexico Territory consisted of most of Arizona and New Mexico (excluding a strip along their southern borders), a small section of southern Colorado, and the very southern tip of Nevada; while the Utah Territory consisted of Utah, most of Nevada, and portions of Wyoming and Colorado. The New Mexico Territory was expanded along its southern extent, to its current border, with the signing of the Gadsden Purchase Treaty on December 30, 1853, which was ratified by the U.S. Congress, with some slight alterations, in April 1854.
  The Colorado Territory was organized on February 28, 1861, created out of lands then currently in the Utah, Kansas, Nebraska, and New Mexico territories. The Nevada Territory was also organized in 1861, on March 2, with land taken from the existing Utah Territory. Initially, only the western 2/3 of what is currently the State of Nevada was included in the territory, with its boundary to the east being the 116th meridian, and to the south the 37th parallel. In 1862 Nevada's eastern border shifted to the 115th meridian, and finally to its current position at the 114th meridian in 1866. The boundary modification in 1866 also included adding the southern triangular tip of the present-day state, taken from the Arizona Territory.
  From July 24–27, 1861 a Confederate force under the command of Lt. Colonel John Robert Baylor forced the surrender of the small Union garrison stationed at Fort Fillmore, near Mesilla, New Mexico. On August 1, 1861, Baylor declared the creation of the Arizona Territory, and claimed it for the confederacy, with Mesilla as its capital. The territory, which had been formed by the portion of the existing New Mexico Territory below the 34th parallel, became official on February 14, 1862.
  Nevada was admitted to the Union on October 31, 1864, becoming the 36th state. This was followed by the admittance to the Union of Colorado, which became the 38th state on August 1, 1876. Confederate Arizona was short-lived, however. By May 1862 confederate forces had been driven out of the region by union troops. That same month a bill was introduced into the U.S. Congress, and on February 24, 1863 Abraham Lincoln signed the Arizona Organic Act, which officially created the U.S. Territory of Arizona, splitting the New Mexico Territory at the 107th meridian.
  Utah, as shown above, evolved out of the Utah Territory, as pieces of the original territory created in 1850 were carved out: parts were ceded to Nevada, Wyoming, and Colorado in 1861; another section to Nevada in 1862; and the final section to Nevada in 1866. In 1890, the LDS church issued the 1890 Manifesto, which officially banned polygamy for members of the church. It was the last roadblock for Utah entering the Union, and on January 4, 1896 Utah was officially granted statehood, becoming the 45th state.
  In 1869, John Wesley Powell led a 3-month expedition which explored the Grand Canyon and the Colorado River. In 1875, he would publish a book describing his explorations, Report of the Exploration of the Columbia River of the West 
caption: United States 1850–1853
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