In May 1520, Müntzer was able to capitalize on the recommendation made by Luther a year earlier, and stood in as temporary replacement for a reformist/humanist preacher named Johann Sylvanus Egranus at St Mary's Church in the busy town of Zwickau (population at that time ca. 7,000), near the border with Bohemia. Zwickau was in the middle of the important iron- and silver-mining area of the Erzgebirge, and was also home to a significant number of plebeians, primarily weavers. Money from the mining operations, and from the commercial boom which mining generated, had infiltrated the town. This led to an increasing division between rich and poor citizens, and a parallel consolidation of larger manufacturers over small-scale craftsmen. Social tensions ran high. It was a town which, although exceptional for the times, nurtured conditions which presaged the trajectory of many towns over the following two centuries.