Schlesinger died Wednesday night at New York Downtown Hospital of a heart attack, after being stricken at a restaurant, his son Stephen told the New York Times.
Schlesinger was also a two-time National Book Award winner. He wrote detailed accounts of the administration of U.S. presidents Andrew Jackson and Franklin Delano Roosevelt, and the notes he took at the Kennedy White House formed the basis for "A Thousand Days: John F. Kennedy in the White House" -- which won both the Pulitzer and the National Book Award.
Schlesinger worked on the presidential campaigns of both John F. Kennedy and Robert F. Kennedy, and some critics said he had difficulty separating history from sentiment, the Times said.
A leader of anti-Communist liberals, Schlesinger was also a fierce partisan, the Times said, who called for the impeachment of President Richard Nixon and denounced the impeachment of President Bill Clinton.
In his final book -- "War and the American Presidency" in 2004 -- Schlesinger called the invasion of Iraq and its aftermath "a ghastly mess."