Miguel Hidalgo y Costilla was a Roman Catholic priest and revolutionary leader who is best known for his role in initiating the Mexican War of Independence in 1810. His famous 'Grito de Dolores' rallied the people of Mexico to rise against Spanish colonial rule, marking the beginning of a struggle that would eventually lead to Mexico's independence. His actions not only sparked a nationwide movement but also had significant ramifications for regions like New Mexico, which were influenced by the changing political landscape.