North America 1853: Gadsden Purchase
Even as California was being accepted into the Union, a new dispute was breaking out between the US and Mexico. The map used for the Treaty of Guadalupe Hidalgo had been inaccurate, meaning that the central part of the US-Mexican boundary was ambiguous. To solve this issue, the US ambassador James Gadsden arranged for the purchase of the disputed region, signing the Gadsden Purchase treaty with Mexico in 1853.
2 Mar 1853 Washington Territory▲
The United States created the Washington Territory from the northern half of the Oregon Territory.
20 Apr 1853 Santa Anna's last presidency▲
With the support of rebellious conservatives, the exiled former dictator Antonio López de Santa Anna returned to Mexico and retook control of the government.
3 Nov 1853–? Mar 1854 Republic of Lower California▲
US-born filibuster William Walker and his followers captured La Paz, Baja California Territory in the Mexican Republic, and established the Republic of Lower California. They were soon forced to flee to Cabo San Lucas and then Ensenada, before withdrawing from the region completely.
30 Dec 1853 Gadsden Purchase▲
James Gadsden, the United States ambassador to the Mexican Republic, signed the Gadsden Purchase treaty with the Mexican government under Antonio López de Santa Anna, ceding 76,800 square km of land in what is now Arizona and New Mexico to the US. The Purchase was ratified and approved the following year.