Miguel Costilla taught philosophy and theology at the San Nicolas Obispo College; he became a priest in 1792. Joining with others who sought independence from Spanish rule, Costilla helped to plan an armed rebellion. The plot was discovered, but before Costilla could be arrested, he proclaimed Mexico's independence from Spain on September 16, 1810. He rallied local peoples to fight for independence. He became the head of an army of 60,000 Indians and mestizos, or persons of mixed Spanish and Indian ancestry; this insurgent army had several victories before Costilla was captured and executed. Others took up the struggle for independence, which was achieved in 1821, during the era of Simon Bolivar.