‘No measures are taken, nor is any necessary, to ensure that this city is well provided with all supplies; for there are many people who live by this trade, and they take great care to bring each thing in its season and to supply the city with all its needs.’ Thus the writer of a report on Zacatecas in 1608 explained how the city, with a permanent population of 1,500 Spaniards and 3,000 Indians, Negroes and mestizos managed to survive in surroundings largely useless for cultivation. Freighting with wagon trains was one of the earliest secondary occupations to grow up in the north as a result of the discovery of the silver of Zacatecas. Carretas and, soon afterwards, heavier carros had begun to roll over the rough tracks from central Mexico and Michoacán by 1550, carving themselves a permanent road within a few years. Despite the perils of Indian attack, the flow of goods into Zacatecas from the south was thereafter continuous; the lure of high prices made the risk and the hard journey worth while. Areas already producing food-stuffs quickly found themselves able to export to Zacatecas; and patterns of trade were set up which persisted beyond the end of the seventeenth century. The linking of the grain-producing areas of Michoacán with the Camino Real in 1550 is one example. Mendoza encouraged this, since he had been told that the inhabitants of Michoacán wished to cart supplies from the towns of Zitácuaro and Tajimaroa to Zacatecas, and to bring back ores to be refined in Zitácuaro.