Editing 1840s (section)

==== Texas ====
{{main|Texas Annexation|History of Texas (1845–1860)}}

The [[Republic of Texas]] had [[Texas Declaration of Independence|declared independence]] in 1836, as part of breaking away from Mexico in the [[Texas Revolution]]. The following year, an ambassador from Texas approached the United States about the possibility of becoming an American state. Fearing a war with Mexico, which did not recognize Texas independence, the United States declined the offer.<ref>Richard Bruce Winders, [https://books.google.com/books?id=mcc9EciebFYC ''Crisis in the Southwest: The United States, Mexico, and the Struggle over Texas''] (Lanham: Rowman & Littlefield, 2002), p. 41.</ref>

In 1844, [[James K. Polk]] was elected the United States president after promising to annex Texas. Before he assumed office, the outgoing president, [[John Tyler]], entered negotiations with Texas. On February 26, 1845, six days before Polk took office, the U.S. Congress approved the annexation. The Texas legislature approved annexation in July 1845 and constructed a [[Constitution of the State of Texas|state constitution]]. In October, Texas residents approved the annexation and the new constitution, and Texas was officially inducted into the United States on December 29, 1845, as the 28th U.S. state.<ref>Fehrenbach, ''Lone Star'', pp. 264–267</ref> Mexico still considered Texas to be a renegade Mexican state, and never considered land south of the [[Nueces River]] to be part of Texas. This border dispute between the newly expanded United States and Mexico triggered the [[#Mexican–American War|Mexican–American War]].

When the war concluded, Mexico relinquished its claim on Texas, as well as other regions in what is now the southwestern United States. Texas' annexation as a state that tolerated slavery had caused tension in the United States among slave states and those that did not allow slavery. The tension was partially defused with the [[Compromise of 1850]], in which Texas ceded some of its territory to the federal government to become non-slave-owning areas but gained El Paso.