Still, the allure of ethanol has faded a bit. Falling profit margins and rising corn costs had prompted ethanol manufacturers to idle roughly 15 percent of U.S. plants by January. Several plants have started producing again as margins recover.
Farmers in the Dakotas are expected to earn fatter returns from corn than from any other crop in 2013, just as they did in 2012. As a result, analysts expect farmers in both states to sow a record number of corn acres for a second straight year.
"Based on what I am hearing from our clients today, there will be more corn," said Mike Krueger, president of the Money Farm, a crop advisory service near Fargo, North Dakota.
In North Dakota's Red River Valley, the state's best land for corn, economists at North Dakota State University project that farmers will net $176 per acre of corn in 2013, compared with estimated returns of $122 for soybeans and $86 for spring wheat.
South Dakota farmers planted corn on 6.15 million acres in 2012, up 37 percent from 2006. In North Dakota, corn acreage has doubled since 2006 and quadrupled since 2001.
"We've been planting corn in some pretty adverse conditions for several years, and even in a really tough year, we see a better return (on corn) than some of the traditional crops," said Bart Schott, a farmer in Kulm, North Dakota, and a past president of the National Corn Growers Association.
U.S. farmers planted 97 million acres of corn in 2012, the most in 75 years. Iowa was the top state with 14.2 million acres.
The expansion along the northern frontier of the Corn Belt has been possible because of improved seed hybrids as well as a climate that has grown more hospitable to warm-season crops like corn and soybeans.
Average temperatures in North Dakota have been rising for decades, expanding the state's growing season by 12 days over the past century, said Adnan Akyuz, an assistant professor of climatology at North Dakota State University who is also the state climatologist.
The expansion allows corn plants, which depend on sunlight and warmth to develop, more time to photosynthesize, boosting yields.
Increased average precipitation since roughly 1990 and the adoption of no-till farming techniques that conserve soil moisture have also encouraged corn's spread, according to Jerry Hatfield with the U.S. Department of Agriculture's National Laboratory for Agriculture and the Environment in Ames, Iowa.
Annual statewide precipitation in North Dakota averaged 23-1/2 inches (596 millimeters) in the 1990s and 22-1/2 inches (569 mm) in the 2000s, compared with about 20 inches (508 mm) during the 1980s, according to data from Lanworth, a unit of Thomson Reuters.