Rio Rico: The Town That Forgot It Was Part of the United States

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Podcast Transcript

International borders can be very strange things. 

Sometimes they measured down to the millimeter and a heavily marked and fortified. 

Other times they run through desolate areas where hardly anyone pays attention to the actual location. 

The latter was the case with much of the US/Mexican border in the early 20th century, and it caused a great deal of confusion. 

Learn more about Rio Rico, the American town that everyone thought was a Mexican town, and then it actually was, on this episode of Everything Everywhere Daily.

There are all sorts of international borders. Sometimes they use mountain peaks to define a border. Other times, they are just arbitrary straight lines that were drawn on a map that cut through whatever happens to be there.

One of the most common natural features which are used as international borders are rivers. 

For the most part, rivers make for good borders. It is a body of water that is difficult to cross that keeps one side apart from the other. 

However, rivers, too, can have their issues as borders. What, for example, is the status of islands in the middle of a river?  There is a small island in the Bidasoa River which serves as the border between France and Spain. Their solution was actually to have joint custody of the islands. 

It is Spanish territory from February 1 to July 31 and French territory from August 1 to January 31. 

Borders don’t necessarily run down the middle of rivers, either. The Courantyne River, which serves as the border between Suriname and Guyana, is entirely within the territory of Suriname. If someone fishes in the river from the bank in Guyana, they are actually making a border crossing.

The biggest problem with using rivers as borders, however, is that rivers move over time. Almost all rivers will naturally meander, changing their shape. If you remember, back to my episode on Terra Nullius, there are border disputes between Serbia and Croatia because of a river meander. 

This is a very long-winded introduction to get me to the subject of this episode, the Rio Grande, the river which serves as much of the border between the United States and Mexico. 

The Rio Grande was established as the border between the United States and Mexico when Texas became a state in 1845. 

For the most part, that was good enough. The river wound through a desert region with a very low population.  If someone knew where the river was, they knew that one side was Mexico and one side was the United States. 

The problem was in certain sections of the river where the river seriously meandered. There are portions of the river where there the river had ‘S-shaped’ turns. This resulted in lobes of land that was almost totally surrounded by one country, with only a small isthmus that connected to the country it belonged to. 

This was the case in a relatively small tract of land known as the Horcón tract. The Horcón tract was a 413-acre or 1.67 square kilometer bit of land which was surrounded on three sides by Mexico but connected to the United States.  It was located in one of these ‘S-shaped’ meanders in the river. 

While the area did look odd on a map, everything was fine, and there was no controversy or confusion until 1906. 

It was then that the American Rio Grande Land and Irrigation Company decided to cut off one of the meanders to shorten the length of the river. No one on either side of the border ever approved this action. The company just did it and ended up having to pay a steep fine for their actions. 

However, the end result is that the small bit of land that connected the Horcón tract to the United States was now cut off by the new channel of the river. The Horcón tract was now south of the river. 

Normally, when a river bend is cut off naturally, the result is an oxbow lake. In this case, the former river meander, no longer being fed by the Rio Grande, just dried up. 

Moreover, no one set up new border markers after this happened. People just went about their business as before and just treated the Rio Grande as the border. The United States to the north and Mexico to the south.

Fast forward to 1929. 

The United States had ratified the 18th amendment, which made the sale of alcohol illegal, aka prohibition. This made for excellent business opportunities along the border. 

To take advantage of this, the town of Rio Rico was established just over the Rio Grande as a destination for Americans to drink and gamble in Mexico to avoid prohibition. It was conveniently located between the towns of Brownsville and McAllen, Texas.

It was built on the Horcón tract of land, which was now south of the Rio Grand as of 1906.

The town was a success. Americans came across the border to do all of the things that were illegal north of the river. It was said that Al Capone visited, but there is no evidence to support it. 

Eventually, prohibition ended, but the town of Rio Rico continued to exist as a functioning Spanish-speaking, Mexican border community of several hundred people. 

Now the story fast-forwards to 1967. 

James Hill, Jr., a geography professor at Arizona State University, was studying old geological survey maps when he noticed something.  The Horcón, the location of the town of Rio Rico, was still technically part of the United States. 

The reason why has to do with a long-standing principle in international law. When a river serves as a border between two countries, any natural meander in the river is reflected in the border. In other words, when the river naturally changes its course, the border will change as well. 

The problem was the 1906 diversion in the river wasn’t a natural change in the river. It was a man-made change. Moreover, it was an unauthorized, private, man-made change. 

That meant that the Horcón tract, which included the town of Rio Rico, was actually part of the United States, which was located south of the Rio Grande. 

The United States and Mexico had previously cleared up one of the biggest outstanding border issues in 1963 with the Chamizal Settlement. This resulted in a small swap of land between the countries in the cities of El Paso and Ciudad Juárez. 

The US and Mexico took steps to rectify the problem with the Boundary Treaty of 1970, which resolved all of the minor border issues between the two countries, including the Horcón tract and the town of Rio Rico. 

The treaty confirmed the reality on the ground that everyone had been living under for decades. Rio Rico officially became a part of Mexico in 1972, and it became a part of the state of Tamaulipas in 1977. 

As an aside, I should note that as of today, there are no outstanding boundary issues between the United States and Mexico, however small. That is not the case between the United States and Canada, which still has a few small issues remaining. I covered them in a previous episode on the US/Canadian border. 

The Boundary Treaty of 1970 didn’t end the story, however. 

In 1972, the United States Immigration and Naturalization Service attempted to deport a man named Homero Cantu Trevino. 

Trevino was born in 1935 in the town of Rio Rico. 

Trevino’s argument was that he was born in the United States and, as such, was a US Citizen and couldn’t be deported. 

The case spent several years going through the courts. The government claimed that Trevino wasn’t a US citizen because the US government did not administer Rio Rico at that time. 

Trevino claimed that it was nonetheless part of the United States, and proof of this was the Boundary Treaty of 1970, where the United States acknowledged it was part of the country at that time.  Furthermore, the federal government paid back taxes to Texas on federally owned land dating back to 1906, acknowledging that the land was part of the United States.

A court ruled in favor of the government in 1976, but the next year a federal appeals court ruled in favor of Mr. Travino and said that anyone born in Rio Rico prior to 1972 was, in fact, a US citizen. 

About 250 people who were born in Rio Rico claimed US citizenship. Each case had to be handled separately, and in some cases, people had to prove what room of a house they were born in. Homes were built on the dried river bed that used to form the border and were technically located in both countries. 

The result of the ruling devastated the town of Rio Rico. Almost everyone who lived there who could prove their birth left and moved north with their newly found American citizenship. 

Moreover, it proved to be an excellent loophole for a whole lot of people in northern Mexico. 

Suddenly, in the 1980s, hundreds of people began to go to Rio Rico to try and get a birth certificate showing that they were born there as it was a free ticket to the US.

The town administrators were very strict about issuing any documentation showing that people were born in Rio Rico because they didn’t want to ruin things for those who actually were born there. 

That didn’t, however, prevent an illegal market from developing for forged birth and baptismal certificates. People not only from Mexico but Europe and even China tried to claim that they had been born in Rio Rico.

Almost all of these attempts were unsuccessful.

Today Rio Rico is just another small border community.  There are some historical markers that indicate the unique history of the town, but that’s about it. 

If you are ever in South Texas or the northern part of the State of Tamaulipas, you can visit Rio Rico. There isn’t much to see, but it does have the distinction of being the only community that was part of the United States and then became part of Mexico.

The Executive Producer of Everything Everywhere Daily is Charles Daniel.

The associate producers are Thor Thomsen and Peter Bennett.

I have a couple of reviews today. The first comes from listener Schooner85 over on Apple Podcasts in the United States. They write:


Love the quick-to-the-point information for so many incredible subjects. Keep up the good work.

Thanks, Schooner. I’ll keep making them if you keep listening. 

The next comes from listener Emmi Metzler over on Spotify. She wrote:

Hello, ?? (Ni Hao),  and ??????? (Vanakkam) from Singapore ??.I have caught up on all the episodes now.

Thanks, Emmi, we can now officially open our completionist club chapter in Singapore. I have a nice spot picked out on Orchard Road, and we will have our own private hawker stand. 

Remember, if you leave a review or send me a boostagram, you too can have it read on the show.