Depicts the seal of the United Mexican States.

The Seal of the United Mexican States is a modified version of the national coat of arms, with the addition of the full official name of the country Estados Unidos Mexicanos, in a semi-circular accommodation in the upper part of the seal. Current and past Mexican peso coinage have had the seal engraved on the obverse of all denominations.

The coat of arms depicts a Mexican golden eagle perched on a prickly pear cactus devouring a rattlesnake. To the people of Tenochtitlan this would have strong religious connotations, but to the Europeans, it would come to symbolize the triumph of good over evil (with the snake sometimes representative of the serpent in the Garden of Eden).

Álvaro Obregón Salido (1880–1928) was a general in the Mexican Revolution, who became President of Mexico from 1920 to 1924. He supported Sonora's decision to follow Governor of Coahuila Venustiano Carranza as leader of a revolution against the Huerta regime. Carranza appointed Obregón commander of the revolutionary forces in northwestern Mexico and in 1915 appointed him as his minister of war. In 1920, Obregón launched a revolt against Carranza, in which Carranza was assassinated; he won the subsequent election with overwhelming support.

Obregón's presidency was the first stable presidency since the Revolution began in 1910. He oversaw massive educational reform (with Mexican muralism flourishing), moderate land reform, and labor laws sponsored by the increasingly powerful Regional Confederation of Mexican Workers. In August 1923, he signed the Bucareli Treaty that clarified the rights of the Mexican government and U.S. oil interests and brought U.S. diplomatic recognition to his government. In 1923–24, Obregón's finance minister, Adolfo de la Huerta, launched a rebellion in part protesting the Bucareli Treaty; Obregón returned to the battlefield to crush the rebellion. In his victory, he was aided by the United States with arms and 17 U.S. planes that bombed de la Huerta's supporters.

In 1924, Obregón's fellow Northern revolutionary general and hand-picked successor, Plutarco Elías Calles, was elected president, and although Obregón ostensibly retired to Sonora, he remained influential under Calles. Having pushed through constitutional reform to once again make reelection possible, Obregón won the 1928 election, but was assassinated by José de León Toral, a Mexican offended by the government's anti-religious laws, before he could begin his second term. Toral's subsequent trial ultimately led to his execution by firing squad, and it also involved a Capuchin nun named Madre Conchita, who was thought to be the mastermind behind Obregón's murder.