After Cortez had defeated the Aztec's in 1521, he was appointed Govenor of Mexico and ruled from 1521-1524. During this time he initiated the construction of Mexico city by destroying the Aztec city of Tenochtitlan and building the new city on top of the ruins. He supported efforts to bring Christianity to the native population, and over the next 7 years tried to establish peace among the Indians of Mexico. He developed mines and farming, imported domestic animals[sheep,cattle,horses] and in 1524 introduced a land tenure system. He appointed men to extend Spanish rule through out the country, was one of the first to attempt to grow sugar in Mexico, and one the first to import African slaves. Within 2 years of the arrival of Cortez, the Aztec Empire had been totally destroyed. Hope it helped :)