Territorial evolution of Mexico

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.

Notes

*Many of the borders of states and territories in northern Mexico remain unclear; the northern border of Sonora, for example, is variously described as either the Gila River or the Colorado River. The list is not impacted by this confusion, but the associated maps could be, and must estimate the borders. The most important issues are:
**Some of the borders of the states in the northern and northeastern extremes prior to Texan independence and the Mexican Cession.
**The extent of Santa Fé de Nuevo México.
*Minor border adjustments with the United States, including the several Rio Grande border disputes, are not shown.

Timeline

;October 4 1824The 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:
# Chiapas
# Chihuahua
# Coahuila y Tejas
# Durango
# Guanajuato
# Jalisco
# México
# Michoacán
# Nuevo León
# Oaxaca
# Puebla
# Querétaro
# San Luis Potosí
# Sonora y Sinaloa
# Tabasco
# Tamaulipas
# Veracruz
# Yucatán
# Zacatecas. The four territories were::# Alta California:# Baja California:# Colima:# Santa Fe de Nuevo México.

;November 18 1824The 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.)

;November 24 1824The territory of Tlaxcala was split from the state of Puebla.

;September 30 1830The state of Sonora y Sinaloa was split into two states, Sinaloa and Sonora.

;May 23 1835The territory of Aguascalientes was split from the state of Zacatecas.

;March 2 1836Due 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 1840Voicing 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.

;November 6 1840The Republic of the Rio Grande rejoined Mexico after a short and failed war of independence.

;September 11 1842The district of Soconusco rejoined Mexico as part of the state of Chiapas.

;December 29 1845The United States of America annexed the Republic of Texas, admitting it as the state of Texas. A large area remains in dispute, helping to trigger the Mexican-American War.

;January 1 1846The state of Yucatán declares independence, for the same reasons as the Republic of Texas and Republic of the Rio Grande, forming the Republic of Yucatán.

;February 2 1848The 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.

;August 17 1848The Republic of Yucatán rejoined Mexico after the Caste War of Yucatán forced them to seek outside help.

;December 30 1853The United States bought the northern strip of Sonora and Chihuahua, measuring 76,770 km², for $10 million, the region now known as the Gadsden Purchase.

;February 12 1857The 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.

;April 29 1863The state of Campeche was split from Yucatán.

;February 26 1864The state of Nuevo León was re-split from Coahuila.

;January 15 1869The state of Hidalgo was split from the state of México.

;April 16 1869The state of Morelos was split from the state of México.

;December 12 1884The territory of Tepic was split from the state of Jalisco.

;November 24 1902The territory of Quintana Roo was split from the state of Yucatán.

;February 5 1917With the promulgation of the 1917 Constitution, the territory of Tepic had its name and status changed to the state of Nayarit.

;February 7 1931The territory of Baja California was split into North Territory of Baja California and South Territory of Baja California.

;November 21 1952The "North Territory of Baja California" changed its status and became the state of Baja California.

;October 8 1974The 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.

References

*cite web |url=http://statoids.com/umx.html |title=Statoids - Mexico States |accessdate=2007-03-14 |author=Law, Gwillim