The donated posters document the studio era of "B" movie filmmaking in the first half of the 20th century and include a variety of genres like westerns, war films, musicals, biblical tales, and social problem films.
The 1,088 posters were donated to the Academy by Dwight Cleveland, a Chicago real estate developer, who continues to collect even today, The Academy said in a statement.
"B-movies tap into the public consciousness and provide rich fodder for better understanding the times," said Margaret Herrick Library Director Linda Mehr.
While Anne Coco, the Herrick's graphic arts librarian, called it a "dream" gift.
"Not only was it very well organized, but the posters also were in excellent shape. Our staff is fairly certain he was a librarian in another lifetime," she said.
Cleveland began collecting in 1977 while still in high school, inspired after seeing film posters in an art teacher's classroom.
"I really think that film posters are one of the very few truly indigenous art forms of our country. By making these gifts, I hope to excite an appreciation for the works themselves among members of the general public and also set a good example for other collectors," Cleveland said.