Between the Gutenberg Bible and the Canterbury Tales, the Beinecke Rare Book and Manuscript Library now has increased its holdings of a different kind of treasure — characters from children’s books.

Announced this fall, the Beinecke is now in possession of the works of children’s author and illustrator Mo Willems. The archive consists of all of Willems’ published work since 2012, as well as some of his drafts, notebooks, toys and games. Future acquisitions will include later works and materials dating from Willems’ time at Sesame Street, prior to the launch of his publishing career in children’s literature.

“[The archive is] mostly notebooks, sketchbooks, ideas, drafts — anything I will no longer use,” Willems said. “The idea is to see the work develop — [the Beinecke] will become a repository for the work as it changes.”

At the archive’s heart are notebooks featuring drawings and ideas related to Willems’ main characters — Pigeon, Knuffle Bunny, Elephant and Piggie. There are several manuscript “dummy” books for Elephant and Piggie and sketches for some of Willems’ earliest comics. The archive also includes the different translations of many of Willems’ published works.

Curator of Modern Books and Manuscripts Tim Young said one of the highlights of the archive are the three Rickshaw sketchbooks. After Willems graduated from college, he spent a year traveling abroad and documented his journey by drawing one cartoon every day.

“It shows him, for a year, working on his drawings and developing a style,” Young said.

Young said the archive is the first of many shipments of Willems’ work the Beinecke will receive. The Beinecke will contact Willems every five years to initiate the process of acquiring more of the author’s works and drafts he will no longer use.

Hosea Baskin ’90, who is the proprietor of Cumberland Rare Books and facilitated the acquisition, said the group of works Beinecke has acquired is substantial. But what is most important about the acquisition is that it begins an ongoing relationship between Willems and the Beinecke, he said.

Plans for the acquisition began a few years ago. Baskin, who lives in the same neighborhood as Willems, knew of the Beinecke’s impressive collection of children’s literature. Willems said he wanted to find a home for some of his drafts and finished works and liked the idea of the papers being in one place.

“The Beinecke is very clear about only wanting dead materials — they only want the stuff that is completely done with,” Baskin said. “Once a book is published and the drafts, manuscripts and sketches are sitting in a drawer, the Beinecke is a better place for them.”

Young said he was interested in obtaining more contemporary, archival materials to complement the Beinecke’s mostly historical collection of children’s literature. Though the Beinecke typically acquires archives of authors who are already in the latter part of their career, Baskin said this was too great an opportunity to miss.

The archive arrived at the Beinecke in 2012. Afterwards, it was catalogued and prepared for use in research. Young said news of the acquisition was delayed until this fall to complement Willems’ return from a yearlong trip to Paris.

Both Young and Baskin said the significance of the archive is far-reaching, as it reveals both Willems’ merit as an author and his creative process.

“Mo has had a meteoric rise in the world of children’s literature — in just over a decade, he has created three pretty iconic series of books,” Baskin said.

Young said Willems writes books that credit the intelligence of children.

Chief Curator and founding Director of the Carle Museum of Picture Book Art Nick Clark said that for example, Willems’ first book — “Don’t Let the Pigeon Drive the Bus!” — gives children the authority to tell the pigeon what to do.

Baskin said Willems’ books and drawings appear simple, but they are thoroughly crafted. His “dummy manuscripts,” he added, exhibit the steps of the creative process.

“Mo would first make a hand-drawn book, where he really worked out the narrative, the flow, the humor and the pacing,” Baskin said. “They’re such a wonderful insight into his working process — to see how the leap gets made from the idea to the book.”

English lecturer Michele Stepto said this new resource provides Yale students with an insight into the creative process of contemporary authors and illustrators.

“I’m looking forward to discovering what connections people make with my work that I haven’t even realized,” Willems said.

Willems began his career on Sesame Street in 1993.