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The Changing Mexico-U.S. Border

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Stretching nearly 2,000 miles from the Pacific Coast to the Gulf of Mexico, the Mexico-U.S. border is the world’s single most crossed international boundary. With over a billion dollars worth of goods moving between the countries every day and 11 million people living within the border region, the history of the Mexico-U.S. boundary line is worth exploring.

The Adams-Onis Treaty. Courtesy of
The Adams-Onis Treaty. Courtesy of Bill Rankin from Radical Cartography.

There are hundreds of years of history of European powers jockeying for position in North America,
but we’re going to skip ahead to the 19th century with the Adams-Onís Treaty. This 1819 agreement between U.S. Secretary of State John Quincy Adams and Spanish Envoy Lord Don Luis de Onís defined the boundary of American and Spanish territories in North America. It established the northern borders of (modern day) California, Nevada, and Utah, followed the Arkansas and Red Rivers, and formed the Eastern edge of Texas, which is the Sabine River.

Mexico declared independence from Spain in 1821 and soonafter became increasingly concerned with the number of American settlers arriving in Texas during the 1820s. Their growing unease about American incursion into their territory came to fruition when U.S. President Andrew Jackson attempted to buy Texas from Mexico in 1829 for five million dollars. The Mexican government flatly refused. Texas, on the other hand, decided it’d rather not be apart of either country and declared their own independence in 1836.

Part of Texas’ creation of The Republic of Texas was establishing new borders with its neighbors. Texas used the Adams-Onís as a boundary line to the U.S., but decided to set the Rio Grande (called the Río Bravo del Norte in Mexico) as its boundary line to Mexico. Mexico, who refused to formally recognize Texas’ independence in the first place, pushed back against Texas’ desire to set their Republic’s border at the Río Grande. Mexico contested that Texas had to move the line back to the Nueces River, which runs through modern day Corpus Christi.

John Disturnell. 1847. "Mapa de los Estados Unidos de Méjico." 9th ed. Geography & Map Division, Library of Congress.
John Disturnell. 1847. “Mapa de los Estados Unidos de Méjico.” 9th ed. Geography & Map Division, Library of Congress.

The dispute surrounding assigning the border at the Río Grande or at Nueces River, coupled with the U.S. annexation of Texas in 1845, set the Mexican-American War into motion. This slice of land between the Río Grande and the Nueces River is called the Trans-Nueces, which you can see in the middle of the two yellow lines in the center of the map on the left. Lasting from 1846-1848, the Mexican-American War ended in the Mexico-U.S. border being set at the Rio Grande and the signing of the Treaty of Guadalupe Hidalgo. As part of the Treaty, Mexico lost a devastating 55% of its land to the U.S., giving both countries the border we recognize today. Well, for the most part.

The problem with setting your border along a natural feature is that natural features can move! The Rio Grande has changed course numerous times, leading to more disputes between both the U.S. and Mexico, and between individual U.S. states. Flooding, falling banks, and land loss were prevalent issues in the decades following the Treaty of Guadalupe Hidalgo and led to complaints from land owners on either side of the Rio Grande. To address the movement, the International Boundary and Water Commission (IBWC) was established to administer treaties and monitor the living border between the U.S. and Mexico. You can get daily updates from the IBWC about flow conditions in the Rio Grande and other related environmental reports about the border that both Mexico and the U.S. care for, together.

J. H. Colton. 1862. "Colton's rail-road and military map of the United States, Mexico, the West Indies, &c." Geography & Map Division, Library of Congress.
J. H. Colton. 1862. “Colton’s rail-road and military map of the United States, Mexico, the West Indies, &c.” Geography & Map Division, Library of Congress.

Comments (19)

  1. So if the President of Mexico decided to listen to Trump and build a wall, would that wall put Texas on the Mexican side since Texas was settled by illegal immigrants? Texas was in Mexican territory when it “declared it’s independence”. I think he would have a case to take the land that was illegally taken by Texas.

  2. Yes, one would think it would still belong to Mexico. You would be correct.❤

  3. So can you please give a short summary of Texas please~~~~~~~~~~~

  4. Texas was NOT settled by illegal immigrants. Texas was settled mostly by U.S citizens but governed by Mexican “authority”.

  5. this was very useful

  6. Take a look at the Big Bend area in Texas using Google satellite which shows the International boundary is a series of straight lines of different lengths that once were aligned with the Rio Grande, a meandering river that doesn’t care about borders. In 2004 I drove to Presidio, Texas and continued on route 170 downstream bordering Big Bend National Park. A few miles out of Presidio, I noticed a Mexican speed limit sign. Only a week ago when I looked at the satellite map which shows the statutory International boundary, did I discover 170 passed through Mexican territory 3 times while U.S. territory at some points extends south of the Rio Grande. If a motorist has a car accident on the Mexican territory and has no Mexican auto insurance, or commits a crime, which nation takes jurisdiction? Beats me!

  7. Mexico gave permission for 300 settlers lead by Stephen F. Austin to establish hies in what is now Texas. Soon they rebelled against tyranny and declared independence and won it at the Battle of San Jacinto lead by Sam Houston

  8. To Lenore, ever heard of annexation? Every settler in the Republic of Texas was granted citizenship. Plus the war. Read up on some Texas revolution and you can understand better.

  9. After Mexican independence the new republic of Mexico was unable to find it’s own to settle Texas because it was isolated and distant, so they allowed Anglo settlers. The Mexican Constitution defines Mexico’s 30 states, islands and federal boundaries, but silent on California, Arizona, New Mexico and Texas, they were very distant from the new nation’s core and Mexico’s interest in frighting for these territories was weak. Mexico was more interested in revolutions amoung their own instead of fighting the enemy.

  10. USA should give Texas back to Mexico

  11. This article establishes President Andrew Jacksons’ offer to Buy Texas – this offer was based upon Andrew Jackson adding land above the 30 degree parallel – this would make Texas a NO-SLAVE STATE – This offer for $5 million was delivered in 1835 – after General Santa Anna had lost to Sam Houston. Santa Anna considered the offer, but turned it down and went back to Mexico. If Texas had become been sold, a western wall which was started by the addition of the Northwest Territories would have covered westward expansion. The Franco-American Treaty of July 4, 1831 was written by France’ anti-slavery hero – the Marquis de Lafayette – it provides $ 6 1/2 Million in gold to America for damages incurred in 1797 – 1799 in an undeclared war – Quasi-War. There is a lot of political history like the Anti-Masonic movement that covered up Masonic – person who had provided the government with anti-slavery activity.

  12. Guard we will not give Texas back to Mexico! You hear me!Texas is the best state ever unlike Mexico!

  13. The United States first obtained jurisdiction or sovereignty of the ceded area of Texas including the Rio Grande River in 1848.

    Under the Compromise of 1850, Texas Southwestern boundary (Rio Grande River) was established by the United States

    Texas’ annexation as the 28th State of the Union was illegal as Texas was a Mexican territory and not a territory of United States. In addition, the joint resolution of Congress was later filed as a treaty. Thus, the House of Representatives didn’t have the authority to vote for annexation as well.

  14. Yes and Texas is the only state that can succeed from the other states and not even the President can do anything to stop it

  15. there is no help here

  16. For the illegal comment above…Texas was Mexico !!!! I’m so tired of folks thinking Mexicans didn’t settle Texas, and that U.S. citizens did. When in fact it was inhibited prior to becoming Texas, Mexico. Then becoming Texas (an independent Republic for a mere 10 years) and then becoming Texas, USA…. you’re not an illegal immigrant if you were already there in Texas before it was Texas, USA (but folks sure like thinking that). And the Mexicans governing it also lived in Texas prior to Americans, Europeans and the Irish showing up. Last but not least, Texas cannot pull away from the U.S.. It can however allow itself to be divided into 6 states, but those states will forever remain in the U.S. Unless of course someone else decides to take it back. Please read more history prior to making yourself look silly.

  17. Current Supreme Court precedent, in Texas v. White, holds that the states cannot secede from the union by an act of the state. More recently, in 2006, Supreme Court Justice Antonin Scalia stated, “If there was any constitutional issue resolved by the Civil War, it is that there is no right to secede.”

  18. John—-Texas never had the right to succeed. It had the right of “division”. Texas could decide to split into 5 states instead of staying one state. This was done for representation purposes. Each of the five newly created states would have 2 senators for a total of 10 coming from the states that were formerly “Texas”. That right was null and void after Texas illegally tried to “succeed” (along with the other southern states) from the United States.

  19. Since the territory gained from Mexico had what we call Native Americans before the land became America wouldn’t the Native actually be Native Mexicans??? Just wondering.

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