Republic of the Rio Grande - Texas - Mexico

The Republic of the Rio Grande was organized on January 17, 1840 at a meeting was held at the Orevena Ranch near Laredo.
Jesus de Cardenas was selected as president.
This revolt of the Mexican states of Coahuila, Nuevo Leon, and Tamaulipas was in response to serious dissatisfaction with the government of Mexico under Santa Anna.
During this period of history the Rio Grande (Rio Bravo) was not universally considered the boundry between Mexico and Texas.
Part of these three Mexican States included what is now part of Texas.
Some of the current counties of Texas which were included in the Republic are -
Webb, Zapata, Starr, Hidalgo, Cameron, Willacy, Kenedy, Brooks, Jim Hogg, Duval, Jim Wells and Kleberg, and perhaps some of Nueces.
The capitol was moved to Guerrero, Tamaulipas, for security reasons, and later after March 1840 to Victoria inside the Republic of Texas.
After a number of military reversals and some negotiation the Republic ceased to exist on November 6, 1840.
This revolution was not without consequences to some of the leaders, who literally lost their heads.

(The flag of this short lived Republic.)

There is a museum dedicated to The Republic of the Rio Grande in Laredo, Texas.
The Harlingen, Texas Museum has an exhibit on the Republic of the Rio Grande.

Wikipedia Republic of the Rio Grande page.

Handbook of Texas - on the Republic of the Rio Grande

Republic of the Rio Grande Museum in Laredo, Webb County, Texas.

article on the Republic of the Rio Grande by Webb County Heritage Foundation.