Hemp is an annual crop grown for the production of fiber. It is sown in the spring like small grain and produces a thick stand of slender unbranched stalks, growing usually to a height of 6 to 10 feet. The fiber is found extending the length of the stalk, between the thin bark on the outside and the woody central pith on the inside. To obtain, the fiber the stalks are retted (partially decomposed) and then put through machines that separate the fiber from the rest of the stalk.
Although hemp has been grown in the United States since early colonial days the acreage of this crop has not been very extensive. Due primarily to competition from cotton, jute, sisal and abaca (Manila fiber) domestic hemp production declined until a low of 1,200 acres was reached in 1933. Since 1939, because of the stimulation of an increased demand due to war conditions, production has again increased. In 1942 there were about 7,500 acres grown for fiber in Wisconsin, 5,000 in Kentucky, 600 in Minnesota and 500 in Illinois.
Wilsie, C. P.; Dyas, E. S.; and Norman, A. G.
"Hemp a war crop for Iowa,"
Bulletin P: Vol. 2
, Article 1.
Available at: http://lib.dr.iastate.edu/bulletinp/vol2/iss49/1