In addition to his wife, he is survived by their sons, Nathaniel and Bizu; his mother; his sister, Erica; and his brother, Joshua.
“His journalism was always participatory, and he took readers along for the ride,” Joel Achenbach, a reporter for The Washington Post, said by email on Tuesday. “He climbed masts on sailing ships, rode mules, marched with Confederate re-enactors, and ventured into dive bars in the remote crossroads of America.”
Mr. Horwitz was driven by an antic energy and unquenchable curiosity. While reporting in the Middle East, he lay down on a battlefield to block Iraqi earthmovers from burying Iranian soldiers in mass graves so that their comrades might claim the bodies, the financial journalist Michael Lewis recalled.
He endured a sweat lodge in the Pacific for four hours, all the while feeling as if he were being cooked alive, because, he told an interviewer at Ohio State University in 2009, “I think it’s the sickness of writing that however horrible the experience is, some little voice inside is saying, ‘Yeah, but this is going to be a great story.’ ”
“He was easily bored with conventional explanations,” Mr. Lewis said, “and his restlessness led him to places a normal person wouldn’t get to.”
Mr. Horwitz was a gifted interviewer. In “Confederates in the Attic,” he engaged the only living Confederate widow at the time in a conversation about the future, in which she predicted, “If it’s like it usually been bein’, it won’t be so good.” And for his latest book, following in Olmsted’s footsteps, he got “the drift of things” in the South by cultivating sources in after-hours interviews in dive bars from the Potomac River to the Rio Grande.