Why does the US/Mexico border start off jagged east of El Paso and Juarez but west of those two cities, it straightens out?

11 comments

1. Because from El Paso to the Gulf of Mexico, the US/Mexico border is the Rio Grande River. West of El Paso, there is no river going that direction, so it’s a line decided by a treaty.

2. The border was set after Texas became independent from Mexico. The jagged part follows the Rio Grande in the south and the Red River in the north and the Sabine River in the east. The straight parts are where there aren’t convenient rivers to use as a border.

   After the Treaty of Guadalupe Hidalgo which had Mexico cede Texas to the US and then annexation of the Republic of Texas to the US.

   It was the treaty that set the US/Mexico border at the Rio Grand. The internal borders were later set by Congress.

3. A treaty for a specific latitude and everything above the Rio Grande river.

4. The Canadian border does the same thing. It’s because the borders developed organically and sometimes geographically in the East, and at some point there were treaties that extended them along latitude lines.

   It’s also why a lot of the Western and Midwestern states are so boxy compared to Eastern ones.

5. A river and then no river.

6. The jagged part of the border is the Rio Grande.

7. [Gadsden Purchase](https://en.wikipedia.org/wiki/Gadsden_Purchase)

   That’s what made the weird angles in New Mexico and Arizona.

8. Most of the western section originally followed a river too, but then we realized we had messed up drawing up the treaty to set the border since the Rocky Mountains didn’t end until south of there. So we went back and bought a strip of land (including the city of Tucson) for use as a railroad, resulting in the straight border.

9. Follows the Rio Grande river between Texas and Mexico then after that just straight lines across the landscape to the Pacific Ocean.

10. https://en.wikipedia.org/wiki/Treaty_of_Guadalupe_Hidalgo

11. Follows a river