The Second Federal Republic of Mexico is established.

The Second Federal Republic of Mexico refers to the period between 1846 and 1863, following the collapse of the Centralist Republic and the restoration of federalism. This shift back to federalism was triggered by widespread dissatisfaction with centralist rule, particularly after the disastrous outcome of the Mexican–American War (1846–1848), where Mexico lost nearly half of its territory through the Treaty of Guadalupe Hidalgo. The republic was characterized by deep political instability, as liberals and conservatives clashed over the country’s direction, especially regarding church-state relations, land ownership, and the distribution of power between federal and state authorities.

During this time, Mexico saw frequent changes in leadership and constitutions, reflecting the intense ideological struggle between the Liberal Party, which pushed for reforms to limit the influence of the Catholic Church and modernize the country, and the Conservative Party, which sought to maintain traditional privileges and a strong centralized government. The liberals managed to pass significant reforms, such as the Constitution of 1857, which guaranteed freedoms of speech, press, and religion, while also nationalizing church lands. These reforms led to the Reform War (1858–1861), a bloody civil conflict between liberals and conservatives that left the country politically fragmented and economically weakened.

The republic ultimately came to an end in 1863, when French forces invaded Mexico under the pretext of unpaid debts and, with conservative support, installed the Austrian archduke Maximilian of Habsburg as Emperor, beginning the Second Mexican Empire. Despite its short life and instability, the Second Federal Republic laid the groundwork for many of the liberal reforms that shaped Mexico’s modern institutions, especially in curbing clerical and military privileges while attempting to strengthen the federal structure.