Why is Millions of Cats considered an important American picture book?

Millions of Cats (1928), written and illustrated by Wanda Gág, is considered a classic and important American picture book because it represents a significant contribution to the development of the picture-book field during the interwar period.12

Gág, an accomplished artist known for her dynamic visual style, brought an intense vitality to her work. Her approach to Millions of Cats helped define the standards for the growing genre of children's picture books, moving beyond the didactic or purely sentimental styles that had previously dominated much of American children's literature. By successfully integrating her own illustrations with a compelling narrative, Gág established a model for the "writer-illustrator" that served as a cornerstone for the high-quality picture books that followed in the 1930s and beyond.12