Notwithstanding the revival of manufacturing and domestic trade, the farmers of the grain states found themselves in distressing circumstances. The Ohio Valley was yielding a product far in excess of the demands that existed and each year found a large amount of unmarketable grain left in the fields and granaries. Many foreign nations refused admittance to American food products and though the grain-growing capacity of the United States had increased sixfold since 1790, the annual exports of grain, meat and flour were but little more than the average for the five years from 1790 to 1795. The plantations of the South were drawing much of their subsistence from the northern farms, but they were unable to absorb more than a small fraction of the tremendous surplus that was seeking a market. Agricultural interests sought urgently for relief. Since there was no foreign market for their surplus, they resolved to _create_ a home market. If England would not buy food products from the United States, the United States must refuse to buy manufactures from England, and must, by the establishment of manufacturing industries at home, give rise to a non-agricultural population that would consume the redundant supplies of meat and grain. The problem of attracting capital to manufacturing enterprises, the farmers proposed to solve by the creation of a system of protective tariffs that would check importations and encourage investment in mills and factories at home. Manufacturing industries already in existence were in no apparent need of protection and the shipping interests of Boston and New York and the cotton planters of the South strenuously opposed the protective policy. But the agricultural interests were not to be denied. Under the leadership of Henry Clay, the tariff of 1824 was enacted and the "American System" was inaugurated. In 1828, in response to an appeal, emanating from the woolen manufacturers and seconded by the agricultural interests, still further encouragement was given to home manufactures.