The Mexican Frontier, 1821–1846 published by other historians. This work was supplemented by additional primary materials which he discovered in the archives that allowed him to delve further into certain areas. "The Mexican Frontier" examines the southwestern United States, specifically the areas now known as Arizona, California, New Mexico, and Texas, in the twenty-five years between Mexico's independence from Spain and the beginning of the Mexican–American War. This resulted in the transfer of control of the border areas to the United States. In the early days of the Republic of Mexico, these areas comprised its northern border, including the territories of Alta California and
Mexican War of Independence in his home to discuss whether it was better to obey or to revolt against a tyrannical government, as he defined the Spanish colonial government in Mexico. Famed military leader Ignacio Allende was among the attendees. In 1810 Hidalgo concluded that a revolt was needed because of injustices against the poor of Mexico. By this time Hidalgo was known for his achievements at the prestigious San Nicolás Obispo school in Valladolid (now Morelia), and later service there as rector. He also became known as a top theologian. When his older brother died in 1803, Hidalgo took over as priest for