This map shows raw material distributions in the Indus Valley and adjacent regions. The extensive trade networks of the Harappan Period (2600-1900 BCE) linked distant resource areas to the major cities in the Indus and Ghaggar-Hakra river valleys. Goods were shipped by boat along the rivers or by oxcart overland. The use of seals and sealings appears to have been integral to the development of trade networks. Seal impressions probably identified the owner(s) of goods, and perhaps the contents of the terra cotta vessels they were shipped in. Impressed clay was also used to seal rope or cloth that bound bales of goods.