Almost any farm product produced in the United States can have subsidies attached. In addition to a floor price, the price may be subsidized to a certain fixed price. Corn is just a piece of the whole. 2004 figures:

Feed grains 2.84 millions (sorghum, etc. etc. as well as corn)
Cotton       1.42 millions
Wheat       1.73   "
Rice         1.13   "
Soybeans    610    "
Dairy       295    "
Peanuts      259    "
Sugar         61    "   (both cane and sugar beets)
Oilseeds, tobacco, wool, vegetable oils, honey, etc. etc. 234 millions.

The whole system of subsidies and tariffs restricts the entry of foreign agricultural products. Asian and African countries complain bitterly.
The Americans sell low and collect subsidies- 30% top-up on corn (maize), 50% for rice and cotton. By selling at low prices, the U. S. can control marketing of these products, all paid for by the taxpayer.

Foreign countries are largely denied the American market while they are pressed to buy the American product- rice and sugar the most contentious. So much rice is produced in the Central Valley of California (as well as the region from Arkansas to the Gulf) that the U. S. almost forces its rice on Vietnam, etc., selling on the market at the low third world prices and demanding that the rice be taken if they wish to keep low tariffs for their exports.
Latin America and Africa cannot market their sugars in the U. S. because of the subsidies and tariffs.

In 2002, Bush signed a bill that raises farm subsidies up to 80% a year for the next ten years. The price tag is $180 billion.