She was the first editor at Poetry Magazine, when it was founded in 1912. From her position as editor, she played a role in the development of modern poetry, both as an early publisher and as a supporter of poets such as Ezra Pound, H. D., T. S. Eliot, William Carlos Williams, Carl Sandburg and others.
Additionally, Monroe was a long time correspondent of the poets she supported, and her letters provide a wealth of information on the thoughts and motives of modernist poets.