Minnesota is one of the nation's largest producers of iron ore. Methods developed to use lower-grade ores such as taconite have kept production up in spite of the depletion of once rich high-grade deposits. Granite (from St. Cloud) and sand and gravel production are also among the largest in the country. Wheat, once paramount in agriculture, has been surpassed by corn, soybeans, and livestock. The state is also a leader in the production of creamery butter, dry milk, cheese, and sweet corn.
By the 1950s manufacturing rivaled agriculture as the major source of income in Minnesota. Major industries in the state produce processed foods, electronic equipment, machinery, paper products, chemicals, and stone, clay, and glass products. Minnesota pioneered the development of computers and other high-technology manufacturing. Printing and publishing are also important.
Reforestation and the use of relatively small trees for pulpwood have helped to keep timber one of Minnesota's assets, even though the "big woods" of the early 19th cent. have been to a large extent felled. The state is roughly 30% forestland and has two national forests. The high days of logging in Minnesota, immortalized in the legend of Paul Bunyan, were brief, but they helped build a number of large fortunes, such as that of Frederick Weyerhaeuser.
Also of great importance to Minnesota are its waterways, which have been extensively developed near industrial centers. Locks and other improvements enable Mississippi River barge traffic to pass around the Falls of St. Anthony at Minneapolis. Duluth, at the western tip of Lake Superior, has one of the busiest inland harbors in the United States; the completion of the Saint Lawrence Seaway (1959) made the city an important port for overseas trade.