The treaty for the Gadsden Purchase was signed on December 30, 1853. I’m not sure you can really call December 30 the anniversary, however, because the history is actually a little more complicated. The terms of the treaty were later changed somewhat. A revised version of the treaty was signed in 1854. You can read about it on the web site of the Office of the Historian of the U. S. Department of State.
As anyone who took Arizona history knows, the purchase made the land south of the Gila River to what is now the U.S.-Mexico border part of the United States. The purchase also included contiguous land in New Mexico stretching east to the Rio Grande. According to the Official Web Site of the Gadsden Purchase(!), the purchase encompassed a total of nearly 30 million acres, and the price paid works out to about 33 cents per acre.
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