Last week, I drove with my parents from Houston to San Jose. About 2000 miles in 3 days. We did a couple of great side trips to White Sands National Monument and Chamizal National Memorial in El Paso. Chamizal was particularly interesting. It used to be located in Mexico, but is now part of the U.S. Why? The 1963 Treaty of Chamizal.
Under the 1848 Treaty of Guadalupe Hidalgo, the Rio Grande River is the formal boundary between the U.S. and Mexico for much of the US-Mexico border. However, rivers naturally change their course over time, whether because of erosion, floods, or other natural events. A serious flood in 1864 altered the course of the Rio Grand in the El Paso area, creating a land dispute between the US and Mexico that remained unresolved for nearly 100 years. The land that now constitutes the Chamizal National Memorial had originally been located south of the Rio Grande; however, with the change of the Rio Grande’s course, it was suddenly located north of it. Given that the Treaty of Guadalupe Hidalgo designated the north side as US territory, that might seem to make the Chamizal land US soil. (Similar things happened, but in reverse, on other parts of the Rio Grande.)
On the other hand, under long-standing doctrines governing land ownership related to rivers, ownership should not have changed. Gradual changes of the course of rivers, usually due to gradual erosion of river banks and gradual deposit of land on other parts of river banks (a process referred to as accretion), is deemed to change property boundaries (and thus land ownership). However, as the late Professor Joseph Sax taught me in law school many many years ago, sudden changes of the course of a river, for example when a flood suddenly and drastically changes a river bed and thus the course of a stream (a process referred to as avulsion), do not alter property ownership and land boundaries. Hence, given that the change in the course of the Rio Grande was due to a sudden flood, land ownership was not altered. (There were of course other legal issues involved in the dispute.)
The question of land ownership and the international boundary took almost a hundred years to resolve. Under the Chamizal Treaty, the US and Mexico formally relinquished claims to lands that had switched sides due to the 1864 flood. The US created the Chamizal National Memorial on portions of the land that changed nationality, but left the original boundary markers.
My parents have one foot in Mexico and one in the U.S., had the boundary been there as it was originally negotiated in 1848. (On a more sober note, the current border slat-fence is easily visible and provides an unsettling sight of our current relationship with our neighbors to the South.)
End of short lesson about water law! Below are some additional photos of our visit to White Sands National Monument – a highly recommended park!