Eric L. Haralson 
Encyclopedia of American Poetry: The Twentieth Century [PDF ebook] 

The Encyclopedia of American Poetry: The Twentieth Century contains over 400 entries that treat a broad range of individual poets and poems, along with many articles devoted to topics, schools, or periods of American verse in the century. Entries fall into three main categories: poet entries, which provide biographical and cultural contexts for the author”s career; entries on individual works, which offer closer explication of the most resonant poems in the 20th-century canon; and topical entries, which offer analyses of a given period of literary production, school, thematically constructed category, or other verse tradition that historically has been in dialogue with the poetry of the United States.