The meditative spaces and down-to-earth people of the Midwest were central to Wallace’s writing, as he pushed back the ironic for the heartfelt. And he didn’t produce brilliant work in spite of the more conventional folks surrounding him in Illinois; as his essays and books like “The Pale King” reveal, he was inspired by the Midwest’s sincerity to go beyond America’s cultural snark for truth about its contemporary life, which he found rushed, overstimulated and lonely. At home in Illinois, this tormented genius, wild maximalist and yet somehow earnest moralist of a writer said he felt “unalone and unstressed.”

One morning after the traffic-stopping sunset, I set out for Champaign-Urbana. The college town of 120,000 is where farm kids like my father would try pizza and tacos for the first time. Dad studied at the U. of I. in the ’70s, when Wallace was growing up in Urbana, and for seven years during Wallace’s adolescence, drinking beer was legal at age 19. Dad remembers the city as chaotic then — marijuana wafting, teenagers vomiting, trash piling up.

For Wallace, life was unstructured. I stopped at placid Blair Park, where he and a high school teammate, John Flygare, taught tennis for five summers. They’d collect cash for the lessons, order pizza out of the proceeds, then turn over whatever was left in the cash box to the Urbana Park District every couple of weeks, Mr. Flygare told me. No one monitored. “I see my kids almost assuming their lives are going to stay structured,” he said. “When we were among ourselves, we were just free.” There were no children in the park that morning, a school day. Soccer nets were up now, signs of an organized sport new to Illinois. An older man walked his dogs alone.

Two miles away I walked into the Illini Union, one of the U. of I.’s acres of neo-Classical buildings, positively Roman in their scale. Upstairs was all elegant blond wood, but downstairs reeked of a cheap rec-room, with pizza, doughnuts and tater tots competing for airspace. Aping college students, Wallace and his friends often played pool on one of the many tables, now orange-felted, Mr. Flygare said. The teenagers were always in a pack; not so today. A student whose blue hair was gelled up like a unicorn horn fired up an “In the Groove” dance game solo.

Other times the Urbana tennis teammates smoked or drank in hotels or on the road when they drove to tournaments around Illinois, which they entered at will, coach-free. The freedom fostered Mr. Flygare’s autonomy, he told me. Other teammates, he said, found the downside of the wide-openness; one developed a spiraling drug problem.

Wallace, too, later fought depression and addiction. He entered treatment in Boston, according to the Max biography, and joined a 12-step program back in Illinois. He drew on those experiences in “Infinite Jest,” whose high-I.Q. characters struggle with their need for a program and its platitudes. “ ‘Getting in Touch With Your Feelings’ is another quilted-sampler-type cliché that ends up masking something ghastly deep and real, it turns out,” Wallace wrote of an alter-ego character, Don Gately, who relives traumas in recovery. “It starts to turn out that the vapider the A.A. cliché, the sharper the canines of the real truth it covers.”