This is a timeline of the territorial evolution of the borders of Mexico, listing each change to the internal and external borders of the country.
October 4 1824 The 1824 Constitution of Mexico was enacted, creating the United Mexican States and replacing the Mexican Empire, which had collapsed on March 19 1823. The constitution organized the country into 19 states and four territories. In the aftermath of the end of the empire, Central American regions mostly voted not to stay a part of Mexico, with Chiapas, formerly part of Guatemala, being the only area that favored remaining in Mexico. However, rebels in one part of Chiapas, Soconusco, proclaimed its separation from Mexico on July 24 1824, and it was formally annexed by the Federal Republic of Central America on August 18 1824.
The founding states were:
The four territories were:
November 18 1824 The Federal District (Distrito Federal) was created around Mexico City (Ciudad de México), separating it from the state of México. Its original dimension was a 8.38 km perfect circle around the Plaza de la Constitución for a total area of 220 km². (This was later increased to 1,700 km² in 1854 by President Antonio López de Santa Anna, and subsequently reduced under President Porfirio Díaz to its present 1,479 km² between 1898 and 1902. This map shows only its modern extent.)
March 2 1836 Due to disapproval of the government of Antonio López de Santa Anna, the Tejas region of the state of Coahuila y Tejas declared independence. The remainder was renamed simply Coahuila. The Treaties of Velasco would signify the end of the Texas Revolution on May 14 1836, creating the Republic of Texas.
January 17 1840 Voicing the same concerns as Texas, the states of Coahuila, Nuevo León, and Tamaulipas declared independence from Mexico as the Republic of the Rio Grande; since the border of Texas was never conclusively decided, they claim a northern border of the Nueces River, while Texas claims a southern border of the Rio Grande.
February 2 1848 The Treaty of Guadalupe Hidalgo formally ended the Mexican-American War, forcing great concessions on Mexico. All disputes with Texas are abandoned; the border between the U.S. state of Texas and Mexico is set at the Rio Grande, officially transferring portions of Chihuahua, Coahuila, and Tamaulipas to the United States. Furthermore, the United States received what is now referred to as the Mexican Cession, equivalent to all of the territories of Alta California and Santa Fe de Nuevo México.
February 12 1857 The 1857 Constitution of Mexico was adopted, reorganizing some states. Nuevo León is merged into Coahuila; Aguascalientes, Colima, and Tlaxcala all had their status changed from territory to state; and the state of Guerrero was created from portions of México and Puebla.
October 8 1974 The territory of Quintana Roo changed into a state status. The South Territory of Baja California changed its status and became the state of Baja California Sur, giving Mexico its present-day configuration.