Claim: Youth and the Bright Medusa, a book by Willa Cather, was published by Alfred A. Knopf (founded in 1915) while Cather was still under contract with Houghton Mifflin.
Evidence: Youth and the Bright Medusa is a collection of short stories by Willa Cather, published in 1920. The book was the first book Cather published with Alfred A. Knopf. Alfred A. Knopf 1915; 105 years ago (1915) Cather was still under contract with Houghton Mifflin for her novels so Knopf offered to put out a selection of her short stories.