When we speak of the U.S.-Mexico border, formally established in 1848, we have to consider that it’s both a physical space as well as an ideological representation of two different places. For much of its history, humans flowed somewhat seamlessly through this physical space.


The following timeline represents some of the most significant dates that have gradually transformed life along the U.S.-Mexico border up to the present day. Thank you to SMU Mission Foods Texas-Mexico Center Faculty Adviser Neil Foley and Center Manager Jenny Apperti for this thorough research.


1848: The Guadalupe-Hidalgo Treaty, ending the Mexican-American war, established that Mexico ceded 55% of its northern territories to United States and relinquished its claims to Texas. It altered the boundaries between the U.S. and Mexico and established the division between both countries, as we now know it.


1849: The Treaty of Guadalupe Hidalgo established the Mexican-United States Boundary Commission to survey and mark the boundaries between the countries. They established the line from the Pacific Ocean to the junction of the Gila and Colorado Rivers in present day New Mexico and Arizona.


1855: The late 1840s and early 1850s brought impasses in negotiations in terms of establishing a physical border. The most notable historical episodes of this time are the Chamizal Dispute and the Gadsden Purchase. After such episodes, the Mexican-United States Boundary Commission finished its work in 1855 and the border now had obelisks monuments separating the two countries.


1882: The Chinese Exclusion Act became the first federal law proscribing entry of an ethnic working group on the premise that it endangered the order of certain localities. Despite that, many Chinese immigrants soon started to enter the U.S. through Mexico thus marking the first time that a type of U.S. immigration was considered “illegal.”


1891-1894: The International Boundary Commission was created to resurvey and remark the boundaries. Obelisks were reconstructed and new ones were erected. During this period, the number of monuments went from 52 to 258.


1911: The first ever border fence was completed. The Bureau of Animal Industry ordered the construction of the fence in order to keep cattle in Mexico from entering the U.S. as a form of prevention following widespread cattle tick disease.


1917: Immigration Act of 1917. This was the second law, after the Chinese Exclusion Act of 1882, aimed at restricting immigrants to the U.S. Now, in order to be able to cross the U.S.-Mexico Border, people had to pay $8 per person and pass a literacy test.


1924: The Border Patrol was created and with it, enforcement of the regulations along the border became stricter.


1930s: During the Depression, feelings of hostility towards immigrants increased. The Federal Government passed laws imposing restrictions and penalties for hiring immigrants.

Over 1 million people were “repatriated” to Mexico during this period. It’s now estimated that about 60 percent of the people in the Mexican repatriation drive were U.S. citizens of Mexican origin.


1942: The U.S. and Mexico signed the Mexican Farm Labor Agreement, better known as the Bracero Program. Even though the program was not without controversy, it managed to regulate Mexican guest workers in the U.S. In a 22-year-time-span, 4.6 million contracts were signed, making it the largest U.S. contract labor program. This era also marked a rise in illegal immigration, as many workers who were not qualified to participate in the Bracero Program crossed the border illegally and found work with growers who wanted to keep their costs low.


1954: Operation Wetback: This immigration initiative was created to deal with illegal border crossings by Mexican nationals into the U.S. The operation consisted on Border Patrol agents locating, processing and deporting Mexicans who had entered the U.S. illegally. An estimated 1,074,277 people were returned to Mexico, half a million from Texas alone.


1965: Immigration and Nationality Act of 1965. Also known as the Hart-Celler Act, it changed the way immigration quotas were allocated in the United States. The new system maintained per-country limits but also created preference visa categories that focused on immigrants’ skills and family relationships with citizens or U.S. residents. This law also brought numerical limits to immigration from Mexico and Latin America for the first time.


1982: The peso was devalued repeatedly during Mexico’s economic crisis. High unemployment pushed more migrants to find work in the United States. That same year, the U.S. Supreme Court ruled that children who were illegal residents had the right to public school education.


1985: Maquiladoras, factories in Mexico run by foreign countries, continued to expand along the border towns, assembling goods for the U.S. market. By the mid-1980s, the total alien population was estimated to be nearly 5 million, and in 1986, the border patrol reported a record 1.7 million apprehensions of undocumented Mexican immigrants.


1986: Immigration Reform and Control Act (IRCA). This law intended to increase border security and establish penalties for employers who hired unauthorized immigrants. Employer sanctions marked a change in immigration policy towards employer responsibility in fueling illegal immigration. It also held the promise of legal status and eventual citizenship to millions of unauthorized immigrants, making it the first large-scale legalization program in U.S. immigration history.


1990s: Operations Hold-the-Line, Gatekeeper and Safeguard. Operation Hold-the-Line was launched on the U.S.-Mexico border in El Paso. Four hundred agents and vehicles were stationed every 100 yards in order to prevent illegal crossings. Operation Gatekeeper was launched in San Diego and Operation Safeguard in Arizona with the same intent. These operations marked a shift in immigration from policies focused on deporting immigrants who had already crossed the border to preventing illegal entries at the border. This period also saw an increase of human smugglers commonly known as coyotes or polleros and the construction of fourteen miles of a border fence between San Diego and Tijuana. In 1994, Mexico again devalued the peso and went through another massive economic crisis, giving rise to the number of Mexican people wanting to migrate to the U.S.


2006: Secure Fence Act. This law authorized the construction of hundreds of miles of additional fencing along the border. By 2011, 649 miles of fencing and vehicle barriers from California to Texas had been erected.


2015: The U.S. Government completed the 652-mile-long border fence.


2016: The number of Mexican immigrant population in the United States shrunk by 300,000. More Mexican immigrants have returned to Mexico than migrated to the United States, and apprehensions of Mexicans at the U.S. border are at a 40-year low. Mexico is no longer the top origin country among the most recent immigrants to the U.S.


2018: Central American Migrant Caravan. More than 7,000 undocumented Central American immigrants walked through Mexico and arrived at the U.S.-Mexico border attempting to cross into the U.S., fleeing persecution and extortion by criminal gangs or the economic conditions in their home countries. The U.S. deployed over 5,000 troops to the border previous to their arrival and added wiring into certain portions of the existing fence. With conditions to cross increasingly difficult, several have decided to stay in Mexico, particularly in Tijuana. More than 1,000 of these migrants have found jobs or been cleared to work in Mexico and 3,500 others have registered for visas. At least 600 have applied for asylum in Mexico.