Grain played an important role in the economy of colonial North America. A. Trade between neighbors was necessary to satisfy the local demand for grain and other products. B. Large amounts of grain from the countryside were brought to cities and ports, both for the residents' use and for the export trade. C. Merchant mills required large economic investments that were not available locally. D. Long-distance trade eventually replaced the need for local trade. E. Wheat farmers were attracted to the export trade because it allowed them to find the best price and because the cash it provided could be used for goods not available locally. F. After some time, cash replaced the trade system and individual account books disappeared.