Editing Gadsden Purchase (section)

== Desire for a southern transcontinental rail line ==
[[File:Arizona Relief NED.jpg|thumb|right|Shaded relief map of Arizona, Basin and Range region to the south, in shades of green]]
As the railroad age evolved, business-oriented Southerners saw that a railroad linking the South with the Pacific Coast would expand trade opportunities. They thought the topography of the southern portion of the original [[Mexican Cession]] was too mountainous to allow a direct route. Projected southern railroad routes tended to veer to the north as they proceeded eastward, which would favor connections with northern railroads and ultimately favor northern seaports. Southerners saw that to avoid the mountains, a route with a southeastern terminus might need to swing south into what was still Mexican territory.

The administration of President Pierce, strongly influenced by Secretary of War [[Jefferson Davis]], a Southerner from Mississippi, saw an opportunity to acquire land for the railroad, as well as to acquire significant other territory from northern Mexico.<ref>{{harvp|Nevins|1947|p=84}}</ref> In those years, the debate over slavery in the United States entered into many other debates, as the acquisition of new territory opened the question of whether it would be slave or free territory; in this case, the debate over slavery ended progress on construction of a [[Transcontinental railroad#Subsequent transcontinental routes|southern transcontinental rail line]] until the early 1880s, although the preferred land became part of the nation and was used as intended after the Civil War.<ref name=Robersonp180 /><ref name=Klugerp504 /><ref>{{cite web |url=https://www.nps.gov/amis/learn/historyculture/str.htm |title=The Southern Transcontinental Railroad |location=Amistad, Texas |publisher=National Park Service |date=February 24, 2015 |access-date=July 8, 2018}}</ref>