The CAMBRIDGE INTRODUCTION TO TWENTIETH-CENTURY AMERICAN POETRY by Christopher Beach is a brief, but rich overview of the subject.
The author starts with the pre-Modernist poets, who came of age in the late 1800s. These tended to write fairly irrevelant verse in imitation of classical models. Their adherence to norms doesn't mean they were audience-friendly -- rather, they were ignored by the bulk of contemporary American society, who was looking to the novel as the best literary form for the young nation. Then Eliot and Pound get substantial attention. Although these two poets and some of their peers chose to settle in Europe, they continued to reflect on their American upbringings and inspire younger poets back in the US. One strong point of Beach's overview is that he discusses some of the female poets of the Modernist era who have been overlooked in anthologies until now.
After the Modernist stream, the American tradition was in delta. Beach organizes the poets he describes by various schools: the Harlem Renaissance, the Beats, the confessional movement, the New Criticism, etc. The Ashbery, O'Hara and the Language Poets are the last to be described in the book. Very little from the 1980s is discussed, and nothing from the 1990s, though this Cambridge Introduction was published in 2003. It's inexplicable that the author overlooked Jorie Graham, who won a Pulitzer in 1996 for her book THE DREAM OF THE UNIFIED FIELD and has sold more than most other American poets.
In spite of that gap, however, I found this an informative volume. I have a wide knowledge of the subject, and I found coverage of every pre-1990s figure I was familiar with. On the other hand, Beach has introduced me to some figures I've neglected until now, and I look forward to discovering their poems.