Gadsden Purchase

The 1854 U.S. acquisition from Mexico of land in present-day southern Arizona and New Mexico. It established much of the modern U.S.–Mexico boundary and enabled plans for a southern transcontinental railroad.

James Gadsden: A U.S. diplomat and railroad advocate who negotiated the 1853 treaty acquiring land from Mexico. As minister to Mexico, he negotiated the agreement that bears his name.
Treaty ratification: The formal approval of an international agreement by a state's designated authority. The U.S. Senate amended and ratified the agreement before the transfer took effect.
Transcontinental railroad: A railway route crossing a continent and connecting distant regions by rail. A southern route across the acquired land was a major motive for the purchase.
Louisiana Purchase: The 1803 U.S. acquisition of a vast territory from France, doubling the nation's area. Unlike the vast Louisiana acquisition, this purchase added a comparatively small southwestern tract.
Treaty of Guadalupe Hidalgo: The 1848 treaty that ended the Mexican–American War and transferred extensive Mexican territory to the United States. Its unsettled boundary and railroad questions helped prompt the later purchase.
United States Senate: The upper chamber of the United States Congress, with constitutional authority to consent to treaties. Senators reduced the proposed area and approved the treaty in 1854.
Southern Pacific Railroad: A railroad company that built and operated major lines across the southern United States and western states. Its later route crossed territory included in the purchase, realizing part of the southern rail vision.
Adams–Onís Treaty: The 1819 agreement in which Spain ceded Florida to the United States and defined boundaries in North America. It settled an earlier U.S.–Spanish boundary, while the Gadsden agreement adjusted a U.S.–Mexico boundary.
Mexican–American War: A war between the United States and Mexico from 1846 to 1848, ending with major Mexican territorial losses. The war created the territorial settlement whose boundary the purchase later adjusted.
Boundary commission: A body appointed to survey, mark, or administer an agreed boundary. U.S. and Mexican commissioners translated the treaty line into surveyed boundary markers.

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