Mexico has experienced many changes in territorial organization during its history as an independent state. The territorial boundaries of Mexico were affected by presidential and imperial decrees. One such decree was the Law of Bases for the Convocation of the Constituent Congress to the Constitutive Act of the Mexican Federation, which determined the national land area as the result of integration of the jurisdictions that corresponded to New Spain, the Captaincy General of Yucatán, the Captaincy General of Guatemala and the autonomous Kingdoms of East and West. The decree resulted in the independence from Spain.

Organizations Subdivision by intendancies

During the period of the Independence of Mexico, part of the territorial organization of New Spain was integrated into the new nation of the Mexican Empire. Added to this were the Captaincy General of Yucatán and the Captaincy General of Guatemala (whose annexation was a strategy to counteract the Spanish crown). This yielded Mexico's largest land area as an independent nation.

Subdivision by state and territory During the structuring of the Republic, territorial and legal changes reaffirmed the Catholic Church's status as the only religion for Mexicans. The new nation developed a popular and representative federal republic that recognized the sovereignty of the States constituting the federal union.

Subdivision by department The liberal government of Antonio López de Santa Anna, influenced by conservatives, ratified the Seven Laws by presidential decree, establishing a new territorial court and replacing the federal states by departments whose governors and legislators would be selected by the President. This break from federalism brought Mexico its most turbulent and unstable era.

During the Second Mexican Empire, Emperor Maximilian I of Mexico made a new division of national territory.

Territorial divisions throughout Mexican history were generally linked to political change and programs aimed at improving the country's economic and social development. On 3 March 1865, one of the most important decrees of the government of Maximilian, the first division of the territory of the new Empire, was issued and published in the Journal of the Empire on 13 March. The reorganization was accomplished by Manuel Orozco y Berra (1816–1881) and was made according to the following rules:

The total land area of the country will be divided into at least fifty departments. Whenever possible, natural features will be used for boundaries. The surface area of each department will take into account the terrain, weather, and all elements of production, so that (eventually) the departments will hold an equal number of inhabitants.

This division was of great importance because geographical features and projected development were taken into account for the delimitation of the jurisdictions. The territorial division of the Second Mexican Empire was used for a short period because the Empire was overthrown in early 1867 with the execution of Maximilian I. The Federal Republic, and its former divisions, were restored in that year.

Clarifications Several of the former borders of the states and territories in northern Mexico remain unclear. The northern border of Sonora, for example, is described in various ways, either as the Gila River or the Colorado River. The list of acts is not affected by this confusion, but the associated maps contain the following uncertainties and omissions:

The territorial extent of the Santa Fe de Nuevo México Territory The exact date that the division between Durango and Chihuahua stopped being a straight line Several minor adjustments to the border with the United States, including the Chamizal dispute, are not specified The Republic of Baja California and Republic of Sonora – proclaimed by the American William Walker in 1854, were never more than a declaration and are not shown on maps. The following maps do not show the separation of Zacatecas (in 1835) and Tabasco (in 1841–1842), which never became independent republics and were never proclaimed as such. The maps do not show the claim of Mexico on part of the former British Honduras, presently known as Belize.

Territorial evolution of Mexico

Timeline

1821–1824 From Independence to the Constitution of 1824 Map Date Description The 24 intendencies of the First Mexican Empire were: Las Californias México Nuevo México Texas Nueva Vizcaya Coahuila Nuevo Reino de León Nuevo Santander Sonora Zacatecas San Luis Potosí Guanajuato Querétaro Puebla Guadalajara Oaxaca Mérida de Yucatán Valladolid Veracruz Guatemala El Salvador Honduras Nicaragua Costa Rica Territorial organization under the interim government of Mexico after the establishment of the Republic on May 21, 1823, and before the decree of the Constitutive Act of the Mexican Federation on January 31, 1824 – the period between the end of the First Mexican Empire and the creation of the Federal Republic of the United Mexican States. After the end of the empire, the Central American provinces decided not to be part of Mexico. Chiapas (part of Guatemala) was not yet part of Mexico, while the region of Soconusco proclaimed its independence from Mexico on 24 July 1824, and was formally annexed by the Federal Republic of Central America on August 18, 1824.

1824–1857 From the Constitution of 1824 to the Constitution of 1857 Map Date Description The Constitution of 1824 officially established the United Mexican States.

The Constitution organized the country into 19 states and four territories. The order of the states is determined by the date of accession to the federation, listed in the order in which the constitutional congress of the state was established. The 19 founding states were:

Order Name Date of Admission to Federation Installation date of the Congress 1 1823-12-20 02-03-1824 2 1823-12-20 25-03-1825 3 1823-12-21 01-07-1823 4 1823-12-21 19-03-1824 5 1823-12-22 06-04-1824 6 1823-12-22 21-04-1824 7 1823-12-22 09-05-1824 8 1823-12-23 20-08-1823 9 1823-12-23 14-09-1823 10 1823-12-23 19-10-1823 11 1823-12-23 17-02-1824 12 1824-01-10 12-09-1824 13 1824-02-07 03-05-1824 14 1824-02-07 07-05-1824 15 1824-05-07 01-08-1824 16 1824-05-07 15-08-1824 17 1824-05-22 08-09-1824 18 1824-07-06 08-09-1824 19 1824-09-14 05-01-1825

The four federal territories were:

Alta California Baja California Territory Colima Territory Nuevo México Territory The Federal District was established around the City of Mexico, separating it from the State of Mexico. The Federal District was originally a perfect circle with an area of , centered on the Zócalo (Constitution Square). In 1854, Antonio López de Santa Anna enlarged the Federal District's area to , before it was reduced to the current between 1898 and 1902, during the rule of Porfirio Díaz. This map shows only the current area of the Federal District. The Tlaxcala Territory was created out of part of the state of Puebla. Sonora and Sinaloa became separate states.

Created as a state.

Order Name Date of Admission 20 14-10-1830 The Aguascalientes Territory was created out of part of the state of Zacatecas. The region of Texas of the state of Coahuila y Texas declared its independence. The rest of the state was named Coahuila. The Treaties of Velasco ended the Texas Revolution on May 14, 1836, with the creation of the independent Republic of Texas. Texas published a map claiming the Rio Grande as its border with Mexico and not the Nueces River, the border since the Spanish colonial era. The Mexican Congress rejected the Treaties of Velasco signed by Antonio López de Santa Anna, arguing that Santa Anna had no authority to grant independence to Texas. The states of Coahuila, Nuevo León and Tamaulipas declared their independence from Mexico as the Republic of the Rio Grande, which also took the eastern part of the state of Chihuahua. However, the border with Texas was never determined: the Republic claimed the Nueces River as its northern border, while Texas continued to claim the Rio Grande as its southern border. The Republic of the Rio Grande returned to Mexico after a brief and unsuccessful war for independence. Coahuila was allowed to keep the part of Chihuahua taken by the Republic as compensation for the loss of Texas. On February 12, 1840, Yucatán sent a report to the central government demanding the restoration of federalism as a form of government to combat poverty in the country. The act demanded the re-establishment of the Mexican Constitution of 1824. On October 1, 1841, the local Chamber of Deputies enacted the Declaration of Independence of the Yucatán Peninsula, thus establishing the second Republic of Yucatán. The region of Soconusco was annexed by Mexico as part of the state of Chiapas, following the dissolution of the Federal Republic of Central America. The U.S. annexed the Republic of Texas and admitted it to the Union as the State of Texas. Mexico did not accept the annexation, while also continuing to claim the Nueces River as its border with Texas. The dispute ultimately provoked the Mexican–American War, which began on April 25, 1846. The Treaty of Guadalupe Hidalgo officially ended the Mexican–American War, forcing large territorial concessions by Mexico. All claims over Texas were abandoned, while the Rio Grande was established as the permanent border between the countries, thus giving portions of the states of Chihuahua, Coahuila, and Tamaulipas to the United States. In addition, the U.S. received what is now known as the Mexican Cession, equivalent to the territories of Alta California and Santa Fe de Nuevo México. Including Texas, Mexico ceded an area of approximately – by its terms, around 55% of its former national territory. On August 22, 1846, interim president José Mariano Salas re-enacted the Constitution of 1824. Two years later, during the government of José Joaquín de Herrera, Yucatán reunited with Mexico. A decisive factor for the reunion was the Caste War, which forced Yucatán to seek outside help. On December 30, 1853, Antonio López de Santa Anna signed a treaty with James Gadsden, the U.S. Ambassador to Mexico, which involved the sale of an area of from the states of Sonora and Chihuahua to the United States for $10 million. This treaty became known as the Gadsden Purchase (and as Venta de la Mesilla in Mexico). The treaty was ratified by the United States Senate on April 25, 1854, and signed by U.S. President Franklin Pierce. Final approval by the Mexican Congress took place on June 8, 1854. After the United States Senate approved the Gadsden Purchase on April 25, 1854, the sale became official. Mexican people angered by the sale proclaimed the Plan of Ayutla, which finally ended the political career of Santa Anna.

1857–1917 From the Constitution of 1857 to the Constitution of 1917 Map Date Description The Federal Constitution of the United Mexican States of 1857 approved the reorganization of the national territory. Nuevo León merged with Coahuila, adopting the name of the latter. Also confirmed were the creation of a new state and the admission of 3 of the 4 territories as free states of the federation.

Created as a state.

Order Name Date of Admission Installation date of the Congress 21 27-10-1849 30-01-1850

Admitted as stated:.