The Rio Grande Border Between Texas and New Mexico
The Niagara River, the Congo, the Tumen River, the Danube. Rivers like these serve as international boundaries all over the world. In some sense, they make borders easy to distinguish—one bank of the river is one country and the other bank is a different country. But rivers meander, change course, and that can cause serious tension and controversy.
The Rio Grande is famous for being the international boundary between the United States and Mexico. But it also serves as the border between Texas and New Mexico for a little over 15 miles, as the crow flies. Whereas the majority of the time rivers act as moving borders, for those 15 miles the Rio Grande has a peculiar case of being fixed to the past.
The Supreme Court Case
The New Mexico-Texas border between the city of El Paso and the town of Anthony seems rather strange at first. It weaves about kind of like a river should, but there is no river that it follows. There is no natural topography at all to explain its irregular pattern. However, the Rio Grande does run along here and it does hold the key to explaining this border.
New Mexico became the 47th US state in January of 1912. As part of the process of admission, the New Mexican Constitution had to outline the state’s borders. For the most part, that was a rather easy process, since New Mexico’s borders are straight lines for every segment besides the one pictured above.
But when it came to the border between El Paso and Anthony, both Texas and New Mexico decided that the border there should follow the path of the Rio Grande as the river ran on September 9, 1850. The trouble was that neither state could definitively prove where that path was.
New Mexico claimed that the Rio Grande ran down the east side of the Mesilla Valley in 1850, pushing its land claims close to the Franklin Mountains. But Texas claimed the river that year ran closer to the center of the Mesilla Valley, a little bit further west than where the Rio Grande runs today. No geological survey existed to determine with certainty which claim was correct.
The dispute ended up in the US Supreme Court. The original suit was brought on by New Mexico in 1913 and it took until 1927 to get a final settlement between the two states.
The Supreme Court ruled in favor of Texas. The key to the case was the testimony of Special Master Charles Warren, who investigated the matter (and several others pertaining to state border disputes) after being asked to do so. He testified to the Court that the path of the Rio Grande in 1850 would have run down the middle of the Mesilla Valley, like Texas claimed.
Thus, that small section of the border between Texas and New Mexico is stuck in history. It weaves about like a river because that is (most probably) where the Rio Grande actually was more than 150 years ago. And although the river moves around and changes path due to its natural tendency to do so, legally, it is stuck in September 9, 1850, forever.