Block died of pneumonia at Sibley Memorial Hospital in Washington.
"Herblock was the greatest cartoonist of all time," said Donald E. Graham, chairman and chief executive of The Washington Post Co., where Block worked.
"His intelligence and his sense of history, combined with his artistic skill helped define many of the key political figures and many of the key events of the last 55 years in Washington," said Graham.
Block's cartoons won three Pulitzer Prizes, and he shared in a fourth for the Post's Watergate coverage. Block's work was syndicated in more than 300 newspapers.
His work was known for its liberal slant and biting humor. Although vicious in black-and-white, he was a gentle soul in person. A friend, cartoonist Chuck Jones, once described him as "a tiger posing as a possum."
His illustrations spanned from the rise of the nuclear peril to the end of the Cold War. It was Block who coined the word "McCarthyism" to describe the redbaiting tactics used by Sen. Joseph McCarthy, and those cartoons were ranked No. 39 on a 1999 New York University list of 100 greatest works of journalism of the century.
He lambasted Richard Nixon for using similar tactics in campaigns for Congress and the vice presidency. In Block's cartoons, Nixon was stoop-shouldered and unshaven, with dark eyes and an evil grin.
When Nixon was elected president, Block began drawing him without the five o'clock shadow - out of respect for the office - but didn't let up his attacks.
"I wouldn't start the day by looking at Herblock's cartoon," Nixon groused to an interviewer.
Block's career began before the stock market crash of 1929 and continued until only recently when he went on vacation. He chronicled every president from Herbert Hoover to George W. Bush.
And Nixon wasn't the only president angered by Block's work. The cartoons prompted complaints from Dwight Eisenhower. Lyndon Johnson canceled a Medal of Freedom ceremony because Block was to be honored. Ronald Reagan lamented, "This guy just doesn't like me," according to one of Block's friends.
But Harry Truman chuckled as he toured an exhibition of Block's drawings. And in 1994, President Clinton awarded him the Medal of Freedom, the nation's highest civilian honor.
Block put on numerous shows and published 10 books of his cartoons, plus an autobiography, "Herblock: A Cartoonist's Life," that he tapped out on a manual typewriter.
He was a lifelong bachelor; friends sometimes said he was married to his work. He spent much of his free time wading through piles of newspapers and magazines and monitoring news broadcasts.
He drew four cartoons a week, down from seven in his early days. Block said he never considered retiring because, "I'd miss it."
"What could be a more enviable or satisfying job than drawing a picture ver day and getting in your two cents' worth on whatever is going on in the world?" he wrote in his autobiography.
His last cartoon appeared in the Post in August, after which he took time off for vacation and fell ill, said Post editorial page editor Fred Hiatt.
Block grew up in Chicago, the son of a newspaperman turned chemist, and took up drawing as a child. He adopted the pen name "Herblock" at age 13, when he started volunteering quips and comments for a humor column in the Chicago Tribune.
At age 19, he dropped out of college to start his first full-time job as a cartoonist at the Chicago Daily News.
From there he moved to the Newspaper Enterprise Association, which mailed his cartoons to papers across the country for 10 years.
Block almost lost the NEA job in 1942 because his cartoons supported Franklin Roosevelt's New Deal and urged America into World War II - opinions his bosses didn't share. But before they could fire him, he won his first Pulitzer Prize.
He was drafted and spent the war in New York drawing cartoons for Army newspapers and posters. Afterward, he settled in at The Washington Post.
With a wooden drawing board perched on his lap, he spent afternoons dashing off drafts of cartoon ideas, then testing them on reporters in the nearby newsroom. The best one was selected to become the next day's cartoon, carefully crafted in pen and ink.
By Jennifer Loven © MMI The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed