The US gained its independence in 1776 from the United Kingdom during the American Revolution and began expanding its territory west. By 1803, Thomas Jefferson acquired a massive portion of land from France by which is referred to as the Louisiana Purchase. The US later purchased Florida from Spain in 1819 while Spain controlled the territory of Texas. However, by 1821, Mexico declared independence from Spain, allocating all of Spanish territory under Mexican control. The US quickly acknowledged the state of Mexico and made diplomatic relations.

With western expansion or what was known as Manifest Destiny, Americans began settling in Texas, a Mexican territory. Not only their presence, but the introduction of slavery to Texas disgruntled the Mexican government as slavery was illegal under Mexican law. By 1835, the Texas Revolution began, creating the Republic of Texas separate from the US and Mexico. However, the southern boundaries were never defined and were heavily disputed between the Rio Grande and the Nueces River.

A decade later, the Mexican government still refused to recognize the Republic of Texas and tensions rose to violence in the Mexican-American War of 1946. By the war’s end, almost half of Mexican territory was ceded to the US including California, Arizona, New Mexico, and Texas. Mexico admitted defeat and relations were stable.

In the 1860’s, Mexico was invaded by France. Benito Juarez and Abraham Lincoln were very similar in personalities as well has policies for their countries. Lincoln aided Juarez to fend off French forces and determined the invasion of France was a violation of the Monroe Doctrine by which the US proclaimed no other states can interfere in the Americas. At the same time this was occurring in Mexico, the Civil War was coming to a close in the US. By its end, the US began to focus more on driving out the French by aiding military supplies to supporters of Mexico and French forces were eventually defeated by 1867.

As relations between the US and Mexico were steady under the dictatorship of Porfirio Diaz, the Mexican Revolution fueled tensions to the brink of war. Radicals by Pancho Villa and others terrorized the border of US and Mexico, threatening the sovereignty of the US by killing citizens on its land. It was also during this time the Zimmerman Telegram, which was a call to arms by Germany to Mexico to engage in battle against the US. The deaths of the revolutionaries ended the war while the US entered WWI in Europe.

Since the Mexican Revolution, the two states have had very good relations. However, issues of immigration, drug trade, economics, and violence have been major points of heated debate. The recently elected PRI Party in Mexico may play a huge role in limiting drug violence. The PRI had been in power in Mexico for 71 years before Vicente Fox of the PAN party was elected in 2000. There is an obvious connection between the switch of parties and the rise of drug violence in Mexico. The PRI had notoriously controlled drug violence by corruption. Many officials in government including law enforcement, military, and politicians were involved in trafficking and benefited from the profits.  When they fell from power, drug issues rose and by 2006, the war on drugs by Felipe Calderon began.