Simont died Saturday at his home in Cornwall, his son, Marc "Doc" Simont, said. He was 97.
With a pared-down style that matched painterly use of color with loose lines, Simont illustrated close to a hundred books over his career. In 1957, he won the Caldecott Medal, one of the top honors in American children's literature, for his illustrations for "A Tree is Nice" by Janice May Udry.
His work also won Caldecott Honor awards in 1950 for Ruth Krauss's "The Happy Day" and in 2002 for "The Stray Dog," based on a story by Reiko Sassa.
Although most were for young people, he worked with authors ranging from Margaret Wise Brown to James Thurber. In 1972, he and author Marjorie Sharmat launched a 21-book series about a boy detective, "Nate the Great."
Simont received some of his earliest training from his father, Jose Simont, a magazine illustrator. He attended schools in Paris, his birthplace, and the National Academy of Design in New York. He settled in the United States permanently when he was 19.
Simont's son remembers watching him work inside his studio in Cornwall, where he bought a house in 1948.
"I saw all of his progress, and I watched him pull his hair out sometimes," he said.
In 1950, Simont began to send cartoons to his local newspaper, The Lakeville Journal.
"Marc was lovely," Cynthia Hochswender, the Lakeville Journal executive editor told The Republican-American of Waterbury. "His cartooning was so gentle but it was quite pointed. He was looking to evoke a strong opinion in the Lakeville Journal, and he succeeded."
Simont won the "James Aronson Award for Social Justice Journalism" Hunter College in 2007 for his political cartoons.