Total agricultural income in 2001 reached $7.5 billion in Illinois, 8th in the nation. Crops accounted for nearly 76% of the value of farm marketings, with corn and soybeans the leading cash commodities.
Prior to 1860, agriculture was the dominant occupation, and food for home consumption was the leading product. Enormous effort was devoted to breaking the thick prairie soil in the northern two-thirds of the state. Fences and barns were erected, and in the 1870s and 1880s the drainage of low-lying areas in central Illinois was a major concern. Commercial agriculture was made possible by the extension of the railroad network in the 1860s and 1870s. Corn, wheat, hogs, cattle, and horses were the state's main products in the 19th century. Since then, wheat and poultry have declined greatly in significance, while soybeans and, to a lesser extent, dairy products and vegetables have played an increasingly important role. The mechanization and electrification of agriculture, beginning about 1910, proceeded at an unmatched pace in Illinois. Strong interest in scientific farming, including the use of hybrid corn, sophisticated animal-breeding techniques, and chemical fertilizers, has also fostered a steady, remarkable growth in agricultural productivity.
The number of farms reached a peak at 264,000 in 1900 and began declining rapidly after World War II, down to 76,000 in 2002. Total acreage in farming was 27.7 million acres (11.2 million hectares) in 2002, down from 32.8 million acres (13.3 million hectares) in 1990. The average farm size has more than doubled from 124 acres (50 hectares) in 1900 to 352 acres (142 hectares) in 1998. The farm population, which averaged 1.2 million persons from 1880 to 1900, declined to 314,000 in 1980; by then, moreover, about half the people who lived on farms commuted to work in stores, shops, and offices.
The major agricultural region is the corn belt, covering all of central and about half of northern Illinois. Among the 50 states, Illinois ranked 2nd only to Iowa in production of corn and soybeans in 2002.
Agriculture is big business in the state, though very few farms are owned by corporations (except "family corporations," a tax device). The financial investment in agriculture is enormous, largely because of the accelerating cost of land. The value of land quadrupled during the 1970s to an average of $2,013 per acre in 1980, fell to $1,536 per acre by 1992, but rose to $2,210 by 1997, and $2,640 by 2002.