Floyd Cooper, a celebrated children’s book illustrator who explored the African American experience in stories rooted in history, like one about a boy in Alabama in 1955 trying to comprehend why a Black woman on his bus refused to give up her seat to a white passenger, died on July 15 in Bethlehem, Pa. He was 65.

His wife, Velma Cooper, said the cause was cancer.

Over 30 years and some 100 titles, Mr. Cooper illustrated children’s stories that not only carried his earthy and golden pastel impressions of Black life, but that also strived to recount chapters of African American history that he felt weren’t taught enough in classrooms — if they were taught at all.

In “Brick by Brick” (2012), he illustrated Charles R. Smith Jr.’s story of enslaved people who toiled to build the White House. In “Juneteenth for Mazie” (2015), also written by Mr. Cooper, a father tells his daughter about the origins of the holiday Juneteenth, which commemorates the end of slavery one June day in 1865. And in “Granddaddy’s Street Songs” (1999), by Monalisa De Gross, an old man spins yarns for his grandson about his past as one of the Black fruit vendors who once traveled around Baltimore on horse-drawn wagons. The story about the boy in Alabama riding with Rosa Parks, “Back of the Bus,” by Aaron Reynolds, was released in 2010.

“To put a book about a little Black child into the hands of a little white child and to put a book about a little white child into the hands of a little Black child,” Mr. Cooper said in a 2016 interview, “it has been something that has been part of my career from the very beginning.”

“Right now,” he continued, “it’s very important that we all get a grasp on what it is that can build bridges between us. I really do see children’s books as a way to build those bridges early on.”

Mr. Cooper’s signature was a subtractive technique that he called “oil erasure,” in which he would wash a board in oil paint and use a rubber eraser to methodically knead the paint away. He’d then create radiant images in soft, shimmering tones.

His work was coveted by acclaimed children’s authors writing about Black life in America, among them Walter Dean Myers, Nikki Grimes, Jacqueline Woodson and Carole Boston Weatherford.

“Floyd’s legacy is that he was storyteller who believed the greatest gift you can give is the truth,” Ms. Weatherford said in a phone interview. “And he believed that children deserved the truth. He didn’t hold it back from them. He believed in filling in the gaps of the African American story, which is to say, the American story.”

“Before there was any national conversation about these things,” she added, “Floyd had been doing that work all along.”

In a fruitful collaboration with the poet Joyce Carol Thomas, he earned finalist citations from the Coretta Scott King Book Awards, which recognize work for children and young adults, for “Brown Honey in Broomwheat Tea” (1993) and “I Have Heard of a Land” (1998). And in 2009 he won the illustration award for “The Blacker the Berry” (2008), which pairs a series of Ms. Thomas’s poems celebrating the diversity of skin color with his illustrations of children as their narrators.

“I feel children are at the front line in improving society,” Mr. Cooper said in a 2009 interview with the Brown Bookshelf, a website dedicated to books for children by Black creators. “This might sound a little heavy, but it’s true.”

Floyd Donald Cooper Jr. was born on Jan. 8, 1956, in Tulsa, Okla. His mother, Ramona (Williams) Cooper, was a beautician. Floyd Sr. built houses. A grandfather had Muscogee Nation, or Creek, heritage, and his family had settled in the area after the forced relocation of tens of thousands of Native Americans from Southeastern states in the 19th century in what became known as the Trail of Tears. Raised in poverty, Floyd grew up in public housing projects, and he attended 11 different elementary schools.

As a boy, while his father labored on a house one day, Floyd picked up a piece of scrap and used it to etch drawings on the home’s exterior. His father rebuked him and told him to scrub them away. By Mr. Cooper’s account it was the start of his subtractive illustration style.

Encouraged by his art teachers, he developed his talents in high school and earned a scholarship to attend the University of Oklahoma, where he studied advertising and graduated in 1978. He became a greeting card designer for Hallmark. But aspiring to illustrate children’s books, he headed to New York in the 1980s, and as he tried to get his portfolio seen by publishers there, he worked as a designer for Olmec Toys, a company that produced multicultural dolls and action figures like Sun-Man.

Mr. Cooper got his break in 1988, when he illustrated Eloise Greenfield’s “Grandpa’s Face.” He went on to write and illustrate his own stories, like “Max and the Tag-Along Moon” and “The Ring Bearer,” and he was drawn to projects involving Black history. In “​​African Beginnings,” he illustrated ancient African civilizations like the Nubian kingdom of Kush, and in “Bound for America: The Forced Migration of Africans to the New World,” he chronicled the Middle Passage.

“I’m from Jamaica,” said his wife, who was Velma Hyatt when she married him, “and when I first came to America and met Floyd I didn’t want to believe what he was telling me about what we had to go through here. Who does these things? But that was his mission. He wanted to educate people about what really happened because they don’t teach this stuff in school. They don’t give the Black perspective.”

In addition to his wife, Mr. Cooper, who died in a rehab facility, is survived by two sons, Kai and Dayton; two sisters, Robin and Kathy; and two grandsons.

Mr. Cooper kept up with the urgent conversation roiling the country about systemic racism and how African American history is taught in the classrooms. Galvanized by the moment, he undertook one of his most personal projects, illustrating “Unspeakable: The Tulsa Race Massacre,” a collaboration with Ms. Weatherford, published this year, that recounts for young readers the destruction of Tulsa’s prosperous Black neighborhood of Greenwood in 1921, an incident that had been largely ignored in history classes.

As a son of Tulsa, Mr. Cooper had long been interested in the massacre. His maternal grandfather had narrowly escaped the carnage.

“Everything I knew about this tragedy came from Grandpa,” Mr. Cooper wrote in a personal note in “Unspeakable.” “Not a single teacher at school ever spoke of it.”

To work on the project, Mr. Cooper shut himself inside his studio and drew feverishly for months. He emerged with illustrations that brought the past back to life.

“It happened in the place where he was born,” his wife said. “His family was involved in what happened. It was his history. It became his last book. He put everything he had into that book.”