Mexico's history extends back to the Mayas, the Toltecs, and the Aztecs, among others. When Spain entered Tenochtitlan in 1519, the days of the Aztecs were numbered. Spain captured the city (now the site of Mexico City itself) and, at its largest, the Spanish empire eventually came to include the land extending from California to Panama, and from the Caribbean to the Philippines. But as Spain weakened in the beginning of the 19th century, the desire for independence on the part of its colonists was heating up. Throughout the 19th and till the mid-20th centuries, dictators vied with reformers, puppets, or heroes for power. A colorful collection of politicians and statesmen have held power in Mexico and while the country has made huge strides economically and politically in the last half-century, it remains a country beset with problems including corruption, a damaged environment, an intermittent brain drain, and occasional guerilla activity on behalf of the Indian populations.