Andy Hall plants corn in a field near Bondurant, Iowa. Less than 1 percent of the U.S. population works in agriculture. (Charlie Neibergall/Associated Press)

In the aftermath of staggering casualties suffered during the bloody Union victory at Shiloh, federal armies were advancing cautiously on the critical Confederate rail center of Corinth, Miss., on May 15, 1862. On the same day in Washington, President Abraham Lincoln signed legislation creating a Department of Agriculture.

The U.S. Department of Agriculture’s birth 150 years ago Tuesday in the midst of the Civil War was part of an enormous expansion of the federal government during the conflict, one that reflected both a response to the great national crisis and a determination by Lincoln to forge ahead with the business of the nation despite the war.

“Agriculture, confessedly the largest interest of the nation, has not a department nor a bureau, but a clerkship only, assigned to it in the Government,” Lincoln had complained in his first annual message to Congress a few months earlier.

Lincoln suggested an agriculture bureau would suffice, but an enthusiastic Congress passed legislation establishing a department to be headed by a commissioner.

“In the midst of a civil war, despite the challenges the country faced, there was a focus on the future,” Tom Vilsack, the 30th U.S. agriculture secretary, said in an interview Monday.

The USDA is marking the anniversary Tuesday with a celebration at the department’s South Building. The agency is touting its efforts in agricultural research, science, improving food supplies and battling food pathogens as work that “fulfills Lincoln’s vision.”

Much has changed in 150 years. At the time, Lincoln noted the United States was lucky that the farming industry “is so independent in its nature as to not have demanded and extorted more from the Government.” Today there are frequent complaints about farm subsidies.

When the department was created, 48 percent of the U.S. population worked in agriculture. Today, the amount is less than 1 percent.

Yet Vilsack argues that agriculture is no less central today to the United States than it was 150 years ago. About 921 million acres were farmed in the nation in 2010, more than twice as many as in 1860.

“We go to the grocery store and see this enormous array of food, and we just take it for granted,” Vilsack said. “We have a tendency to ignore the enormous contribution our agricultural production makes to national security.”

The USDA is holding a series of events marking the anniversary, including a forum held in February on the future of agriculture with Vilsack and eight former secretaries representing every administration since Jimmy Carter’s.

At Tuesday’s event, which will be broadcast at 10:30 a.m. on the USDA Web site, Vilsack will be joined by Joe Scarborough and Mika Brzezinski, co-hosts of MSNBC’s “Morning Joe.” Also participating will be Chuck Leavell, keyboardist for the Allman Brothers and the Rolling Stones, who is a Georgia tree farmer and co-founder of environmental information Web site Mother Nature Network.

Former Washington Redskins Art Monk and LaVar Arrington, who are involved in “Fuel Up to Play 60,” an in-school nutrition and physical activity program supported by USDA, will also give presentations.

Over his desk at the USDA headquarters, Vilsack has a large photograph of perhaps the most famous agriculture secretary, his fellow Iowan, Henry Wallace, who served in the position for eight years during Franklin D. Roosevelt’s administration and served one term as FDR’s vice president. “I look up to him every day,” Vilsack said.

“This is an extraordinary story, and USDA has been at the center of it,” he said.

Lincoln was pleased with the creation, telling Congress a few months before his assassination, “It is precisely the people’s Department, in which they feel more directly concerned than in any other.”