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Jan 1, 1565
1565
Spain establishes its first permanent settlement in the Americas, St. Augustine in Florida. -
1763
After the Seven Years' War (French and Indian War in North America), Spain cedes Florida to Great Britain in the Treaty of Paris. -
1783
With the Treaty of Paris ending the American Revolutionary War, Great Britain recognizes the independence of the United States of America, but the territorial boundaries are not precisely defined. -
1795
Spain reclaims Florida from Great Britain through the Treaty of San Lorenzo (also known as Pinckney's Treaty), effectively ending British rule in Florida. -
1810
The Spanish American Wars of Independence begin, with revolts against Spanish rule in various colonies, including those in the present-day United States. -
1819
The Adams-Onís Treaty (also known as the Transcontinental Treaty) is signed between the United States and Spain, defining the border between the two countries along the 42nd parallel from the Gulf of Mexico to the Rocky Mountains. Spain cedes Florida to the United States. -
1821
Mexico achieves independence from Spain, inheriting territorial claims in the Southwest United States, including Texas and California. -
1829
President Andrew Jackson sends a diplomatic note to Spain demanding the right to deposit the US debt to Spain in the Florida territory, effectively asserting US sovereignty over Florida. -
1835-1836
The Texas Revolution erupts as Texans seek independence from Mexico. -
1845
The United States annexes Texas, which had declared independence from Mexico in 1836 and was recognized by the US in 1837. -
1846-1848
The Mexican-American War is fought between the United States and Mexico, resulting in the United States gaining vast territory, including California, New Mexico, Arizona, Nevada, Utah, and parts of Colorado and Wyoming. -
1848
The Treaty of Guadalupe Hidalgo is signed, officially ending the Mexican-American War and recognizing the United States' annexation of the territory gained during the war. -
1853
The Gadsden Purchase is made, in which the United States purchases a strip of land from Mexico along the southern border of Arizona and New Mexico, including parts of what is now southern Arizona and southwestern New Mexico.