Because of the fertile soil (dominantly brown silty clay loam,) the area around Soest was occupied long before 836 when the village is first mentioned in the "Dagobertsche Schenkung", although the origin of this document is historically uncertain. But there is no doubt that Soest has been inhabited for a long time; excavations in the last two decades have uncovered signs of habitation stretching back more than 4000 years. In the 11th and 12th centuries, Soest grew considerably, making it one of the biggest towns in Westphalia with some 10,000 citizens. It was also an important member of the Hanseatic League until 1609.