The Second Federal Republic of Mexico () is the name given to the second attempt to achieve a federalist government in Mexico after a period of centralism. Officially called the United Mexican States (), a federal republic was established again on August 22, 1846 when interim president José Mariano Salas issued a decree restoring the 1824 constitution. The Second Republic continued to be rocked by the political instability that had characterized Mexico since independence. Mexico's loss in the war with the United States during this time saw half of Mexican territory become part of the United States. Even though Antonio López de Santa Anna played a major role in that loss, he returned to the presidency afterwards, selling further northern territory to the United States. The sale of the Mesilla Valley was for many the final straw, and liberals promulgated of the Plan of Ayutla in 1854, calling for the overthrow of Santa Anna. Santa Anna went into exile and the liberals set about implementing their vision of Mexico.