2014 Survey Pinpoints 1821 Border Between USA and Mexico

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Slideshow includes photos from exhibition at Museo de las Artes, Universidad de Guadalajara, Mexico, courtesy of the Delimitation Survey sponsored by the Museum of Contemporary Art in San Diego, USA

Where was the original border between Mexico and the United States after Mexico gained independence from Spain in 1821?

To pinpoint the exact location, a team backed by a museum in San Diego and guided by GPS information spent weeks in 2014 traveling the original international border. Their findings fill in the blanks created by textbooks that omit or gloss over the boundary between the USA and Spain established by the Adams-Onís Treaty.

The project started with the question, “What would Mexico and the United States look like if that boundary had been fully realized?”

Along their route, team members erected 47 markers to show the original border. Marker #01 is on the Pacific Coast near the state line between California and Oregon. The team erected markers running along northern state lines of Nevada and Utah, across a lower portion of Wyoming, southward through Colorado, Kansas, and Oklahoma, and to Texas and Louisiana. Marker #47 is on the Gulf Coast near the state line between Texas and Louisiana.

During their journey, they encountered dozens of US residents curious about the project and eager to learn more about border history. All were friendly—one woman invited them to erect a marker in her yard, and one man gave them a place to stay one night. “Curious amazement best describes the reactions,” says team member David Taylor.

A narrative included in the exhibit states that only a few people the project team met seemed to grasp that Mexico once encompassed all of present day Arizona, California, Nevada, New Mexico, Utah, Texas, more than half of Colorado, and smaller portions of Wyoming, Kansas, and Oklahoma. One marker is near grain elevators on the edge of Dodge City, which might have become a border town today if not for the Mexican-American War. Who knew?

Many textbooks that marginalize the significance of the 1821 boundary also hide key aspects of the war that took about half of Mexico by military force—one of the largest land conquests in modern military history. This misleads many into thinking the land acquisition was something like the Louisiana Purchase.

“American students might be forgiven if they know little about the Mexican-American War of 1846-1848. It was a conflict not covered in high school history texts until recently,” writes historian and educator Michael Hogan[1]. “When it did finally appear in such texts as a subset of Westward Expansion, the result was to make it look like a fight for freedom on the part of patriotic Texans, migration to the territories, and the subsequent acquisition via the Treaty of Guadalupe Hidalgo.”

“In fact, the Mexican War was a preemptive invasion by US forces with the primary purpose of acquiring California and a land route across the Southwest,” Dr. Hogan continues.

Recently, Dr. Hogan visited the traveling San Diego exhibition in Guadalajara, Mexico, where he taught Advanced Placement US History for several years. Always the professor, he walked friends through the exhibit and discussed the historical significance of the San Diego border delimitation project. The exhibition is touring both the USA and Mexico, and you can click here to see background information.

To help educators and students better understand historical relations between the two countries from 1821-1867, the Lincoln and Mexico Project (LAMP) offers supplemental classroom materials. They include copies of archival documents from both countries that educators can use to facilitate classroom discussion. Many documents examine Abraham Lincoln’s opposition to the war as a one-term congressman, and his legacy of support for Mexico as president.

If you’re an educator, we hope you’ll use the San Diego delimitation project to help your students learn more about US-Mexico border history. And we hope you’ll consider using the LAMP classroom materials to discuss past, present, and future bilateral relations. Just send a request to lamp@lincolnandmexicoproject.org, and we’ll send a complimentary package that includes lesson plans. We look forward to hearing from you.  


[1] Hogan, Michael. Abraham Lincoln and Mexico: A History of Courage, Intrigue and Unlikely Friendships. San Diego:  EgretBooks.com, 2016

Author: LAMP

Co-founder of the Lincoln and Mexico Project. Email: lamp@lincolnandmexicoproject.org. USA: 619-246-4342. MX: +52-33-3676-5897

2 thoughts on “2014 Survey Pinpoints 1821 Border Between USA and Mexico”

  1. Interesting project. If less than completely accurate. Perhaps it is just a matter of Texas doing things differently, but I recall studying the Mexican War in junior high school around sixty years ago.


    1. Thanks for feedback. Part of the purpose of the Delimitations Survey was to use GPS data to accurately pinpoint the 1821 border before Texas declared independence from Mexico. The boundary is based on the Adams-Onis Treaty between USA and Spain in which the USA renounced claims to this vast territory. Textbooks from earlier years ignored the 1821 boundary, and many textbooks even today are not based on treaties or original documents. Best regards.


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