In the Central Valley region of the Southeastern Mexican state of Oaxaca archeologists discovered evidence of historic settlements. Aztecs from Tenochtitlan on the volcanic plateau to the North around what today is Mexico City first arrived in this region around 1250 AD establishing military rule in the 15th century until the arrival of the Spanish. After the fall of Tenochtitlan, the Spanish took over Oaxaca which led to the eventual decrease of the Native population and the increase in African slaves. The region was then settled by mostly Spanish immigrants from Europe and the African slaves they brought with them. Oaxaca was considered a department after the Mexican War of Independence, but after the fall of emperor Agustín de Iturbide, it became a state in 1824 with José Murguia as its first governor. During the 19th century, Oaxaca was split between liberal and conservative factions. The political and military struggles between the factions resulted in wars and intrigues. A series of major disasters occurred in the state from the 1920s to the 1940s. In the 1940s and 1950s, new infrastructure projects were begun. From the 1980s to the present, there has been much development of the tourism industry in the state.