Papal Bull Inter Caetera and the Treaty of Tordesillas (1493-1494)
Many people do not know that when Christopher Columbus "discovered" the Americas, they already legally belonged to Portugal. According to previous papal bulls of the 15th century, Portugal held claim to any and all undiscovered lands west of a certain longitude. After Columbus' return, both Spain and Portugal laid claims to the new lands, forcing the pope to sort things out. Pope Alexander VI issued the bull Inter Calera in 1493, declaring that Spain owned all new lands west of a line 100 leagues (about 300 miles) from the Cape Verde Islands. Portugal, not pleased with the verdict, pressed the issue and the two nations ratified the Treaty of Tordesillas in 1494, which established the line at 370 leagues from the islands. This treaty essentially ceded Brazil to the Portuguese while keeping the rest of the New World for Spain, therefore laying the framework for the modern demographics of Latin America.
The Conquest of the Aztec and Inca Empires (1519-1533)
After the New World was discovered, Spain soon realized that it was an incredibly valuable resource that should be pacified and colonized. Only two things stood in their way: the mighty Empires of the Aztecs in Mexico and the Incas in Peru, who would have to be defeated in order to establish rule over the newly-discovered lands. Ruthless conquistadores under the command of Hernán Cortés in Mexico and Francisco Pizarro in Peru accomplished just that, paving the way for centuries of Spanish rule and enslavement and marginalization of New World natives.
Independence from Spain and Portugal (1806-1898)
Using the Napoleonic invasion of Spain as an excuse, most of Latin America declared independence from Spain in 1810. By 1825, Mexico, Central and South America were free, soon to be followed by Brazil. Spanish rule in the Americas ended in 1898 when they lost their final colonies to the United States following the Spanish-American War. With Spain and Portugal out of the picture, the young American republics were free to find their own way, a process that was always difficult and often bloody.
The Mexican-American War (1846-1848)
Still smarting from the loss of Texas a decade before, Mexico went to war with the United States in 1846 after a series of skirmishes on the border. The Americans invaded Mexico on two fronts and captured Mexico City in May of 1848. As devastating as the war was for Mexico, the peace was worse: the Treaty of Guadalupe Hidalgo ceded California, Nevada, Utah and parts of Colorado, Arizona, New Mexico and Wyoming to the United States in exchange for $15 million and forgiveness of about $3 million more in debts.
The War of the Triple Alliance (1864-1870)
The most devastating war ever fought in South America, the War of the Triple Alliance pitted Argentina, Uruguay and Brazil against Paraguay. When Uruguay was attacked by Brazil and Argentina in late 1864, Paraguay came to its aid and attacked Brazil. Ironically, Uruguay, then under a different president, switched sides and fought against its former ally. By the time the war was over, hundreds of thousands had died and Paraguay was in ruins. It would take decades for the nation to recover.