DePreist, who was 76, had been in and out of the hospital since a massive heart attack last March that was followed by open-heart surgery, his wife, Ginette DePreist, told The Oregonian newspaper.
DePreist was director emeritus of The Juilliard School's conducting program in New York. He was the Oregon Symphony's music director from 1980 until 2003, transforming it from a small, part-time group into a full-time nationally recognized orchestra with 17 recordings.
DePreist also led orchestras in Quebec, Monte Carlo, Tokyo and Malmo, Sweden.
The Oregon Symphony will dedicate its weekend performances to the charismatic conductor known as "Jimmy."
"We are talking about a man with an international career, who achieved many things on international stages," Oregon Symphony conductor Carlos Kalmar said. "And you can only do that if—aside from technicalities—you are a real personality, someone the musicians look up to, and you keep the audiences very, very interested. And I think in that sense Jimmy was great."
Peter Frajola, a principal violinist hired by DePriest more than a quarter-century ago, said the symphony took "phenomenal musical journeys" with the conductor, and his influence went beyond the concert hall.
"A huge figure in the Portland area; everybody knew him," Frajola said. "Even if you weren't a musician, even if you never went to the symphony, you knew who Jimmy was. Everybody loved him. He was just absolutely wonderful speaker to the audience. Made everyone feel welcome."
DePreist was born in Philadelphia in 1936. According to his website, he studied composition with Vincent Persichetti at the Philadelphia Conservatory of Music and earned bachelor's and master's degrees from the University of Pennsylvania.
He contracted polio in 1962 while in Thailand, affecting his walk for the rest of his life. He developed kidney disease in the 1990s and had a transplant in 2001.
In 2005, President George W. Bush presented DePreist with the National Medal of Arts, the nation's highest honor for artistic excellence. The conductor also received more than a dozen honorary doctorates, was honored in countries from Finland to Japan, and managed to write two books of poetry.
DePreist was the nephew of Marian Anderson, a celebrated contralto whose 1939 concert on the steps of the Lincoln Memorial was a landmark moment in civil-rights history. DePreist told National Public Radio in 2005 that that his aunt "was simultaneously the most humble person I ever met in my life and the most powerful."
Though DePreist was a pioneer in terms of African-American conductors, he downplayed that aspect of his career.
"He never seemed to bring that to the foreground," Frajola said. "It was always more important to him to play the music well, to be thinking artistically and to take care of his orchestra."
In a 1992 letter to the editor of the New York Times, in which he responded to an article about minority conductors, DePreist made clear that artistry was his major concern.
"What self-respecting musician would really want to be engaged for reasons primarily other than artistic?" DePreist wrote. "In my view, any orchestra that engages a conductor, soloist or player because that individual is black not only offends the process but also demeans the musician and compromises the artistic integrity of the institution.
"Any prize artificially pushed toward our grasp is a prize not worth having."