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
First Mexican Empire First Mexican Empire The Mexican Empire (, ) was a short lived monarchy, and the first independent post-colonial imperial state in Mexico. It was the only former colony of the Spanish Empire to establish a monarchy after independence. Together with the Brazilian Empire, it was one of two European-style empires in the Americas. The Mexican Empire lasted two years. It existed from the signing of the Treaty of Córdoba and the declaration of Independence of the Mexican Empire in September 1821 until the emperor's abdication in March 1823 when the Provisional Government took power and the First Mexican Republic was