With his brothers, James, John, and Joseph Wesley, he founded the Harper & Brothers publishing house. He is credited with founding Harper's Weekly (1850), Harper's Magazine (1850), and Harper's Bazaar (1867). Fletcher gave cartoonist Thomas Nast his start in Harper's Weekly, and gave Nast great editorial freedom.
He established Harper & Brothers publishing house with his brothers, James, John, and Joseph Wesley. He is credited with founding Harper's Weekly (1850), Harper's Magazine (1850), and Harper's Bazaar (1867). Fletcher provided cartoonist Thomas Nast a launchpad at Harper's Weekly, granting him considerable editorial autonomy.