Federal Constitution of the United Mexican States promulgated

Background. The constitution emerged from the Liberal Reform movement, which had sought to overthrow Santa Anna's dictatorship via the Plan of Ayutla in 1855. President Juan Álvarez resigned in December 1855 amid increasing opposition, passing the presidency to the moderate Liberal Ignacio Comonfort, whom it was hoped could more effectively pass progressive reforms. Meanwhile, the Mexican Congress drafted a new constitution integrating the Ley Juárez and the Ley Lerdo, which had nationalized most of the Catholic Church's properties along with the communal properties of Mexico's Indigenous communities, with the aim of selling them off to stimulate economic development.

Drafting Process. On 16 October, a call was made for a congress to assemble at Dolores Hidalgo in February 1856, to organize the nation under the republican, democratic, and representative form, based upon a decree dating back to the Bases of Tacubaya in 1841. Benito Juárez personally lobbied for a measure expelling the Jesuits from Mexico, passed in June 1856, and the Mexican Congress drafting the new constitution integrated into itself the Ley Juárez along with the Ley Lerdo. The resulting Constitution of 1857 was promulgated on 5 February 1857, with the aim of coming into effect on Mexican Independence Day, 16 September of that year.

Ratification and Controversy. The constitution was ratified on 5 February 1857, establishing individual rights such as universal male suffrage, freedom of speech, and freedom of conscience. However, the clergy threatened excommunication for those who swore allegiance. Pope Pius IX denounced the constitution in December 1856, criticizing the removal of ecclesiastical privileges and the admission of free exercise of all cults.