Marianne Moore garnered significant critical acclaim and public recognition for her poetry during her six-decade career, including the rare triumph of winning poetry's "triple crown" of major awards—the National Book Award in 1952, the Pulitzer Prize in 1952, and the Bollingen Prize in 1953—for her 1951 work Collected Poems. Born in Kirkwood, Missouri outside of Saint Louis, Moore's family moved to Pennsylvania when she was 9. She attended Bryn Mawr College in Pennsylvania, from which she graduated in 1909. During the next decade, Moore began writing poetry in earnest, finally emerging on the national literary scene in 1915, when several major literary magazines first published her poems. In 1918 Moore and her mother moved to New York City, where Moore was to live the remainder of her life. During the early 1920s, Moore worked for the New York Public Library while continuing to write poetry. In 1925 Moore became editor of the prestigious literary magazine Dial, a post she held until the magazine ceased publication in 1929. From that point onward, Moore made her living writing poetry and reviews.

Moore once told an interviewer for the New York Times: "Poetry. I, too, dislike it: There are things that are important beyond all this fiddle. [But,] if you demand on the one hand / the raw material of poetry in / all its rawness and / that which is on the other hand / genuine, then you are interested in poetry."

Moore continued: "I don't call anything I have ever written poetry. In fact, the only reason I know for calling my work poetry at all is that there is no other category in which to put it. I'm a happy hack as a writer. . . . I never knew anyone with a passion for words who had as much difficulty in saying things as I do. I seldom say them in a manner I like. Each poem I think will be the last. But something always comes up and catches my fancy."

In spite of Moore's rather humble thoughts, many critics believe in the significance of her poetry. For example, John Ashbery glowed: "I am tempted simply to call her our greatest modern poet. This despite the obvious grandeur of her chief competitors, including Wallace Stevens and William Carlos Williams. It seems we can never remind ourselves too often that universality and depth are not the same thing. Marianne Moore has no 'Arma virumque cano' prefacing her work: She even avoids formal beginnings altogether by running the first line in as a continuation of the title. But her work will, I think, continue to be read as poetry when much of the major poetry of our time has become part of the history of literature."

Ashbery isn't alone in his praise of Moore's poetry. James Dickey wrote: "Each of her poems employs items that Ms. Moore similarly encountered and to which she gave a new, Mooreian existence in a new cosmos of consequential relationships. What seems to me to be the most valuable point about Ms. Moore is that such receptivity as hers . . . is not Ms. Moore's exclusive property. Every poem of hers lifts us toward our own discovery-prone lives. It does not state, in effect, that I am more intelligent than you, more creative because I found this item and used it and you didn't. It seems to say, rather, I found this, and what did you find? Or, a better, what can you find?"

Nation critic Sandra Hochman agreed: "The art of Marianne Moore is not just the valuable art of observation. She is magical. Her poems do have riddles. They can irk us. But they finally carry us forward by the strength of language and, in her own words, the poet's 'burning desire to be explicit.' Nothing is wasted. All is transformed."

It is this desire that underlies Moore's poetry. James Dickey explained that "Ms. Moore tells us that facts make her feel 'profoundly grateful.' This is because knowledge, for her, is not power but love, and in loving it is important to know what you love, as widely and as deeply and as well as possible. In paying so very much attention to the things of this earth that she encounters, or that encounter her, Ms. Moore urges us to do the same, and thus gives us back, in strict syllables, the selves that we had contrived to lose. She persuades us that the human mind is nothing more than an organ for loving things in both complicated and blindingly simple ways, and is organized so as to be able to love in an unlimited number of fashions and for an unlimited number of reasons. This seems to me to constitute the correct poetic attitude, which is essentially a life-attitude, for it stands forever against the notion that the earth is an apathetic limbo lost in space." As Ms. Moore herself explained to Howard Nemerov: "I am . . . much aware of the world's dilemma. People's effect on other people results, it seems to me, in an enforced sense of responsibility—a compulsory obligation to participate in others' problems."

Marianne Moore is almost as famous for her practice of rewriting her previously published poems as for her poetry itself. This practice has often disturbed many of her followers. Jean Garrigue explained: "Poets who revise their poems are apt to incur surprise or weak query (a guise of protest) from those who have long ago fallen in love with that 'one and only,' the original. The poet, patient about perfection, has a right to be impatient with such resistance. But there it is. And a good deal is involved. A line taken out of a poem sparingly built in the first place, that line's removal subtly alters the whole in tone. An 'excess' excised—a qualifying extension or elaboration—complicated one's responses, for one is busy dismissing and it takes time to adjust to the revision. What is being felt is the absence, almost as much as the new presence."

And Anthony Hecht once wrote that as "an admiring reader I feel that I have some rights in [this] matter. Her poems are partly mine, now, and I delight in them because they exhibit a mind of great fastidiousness, a delicate and cunning moral sensibility, a tact, a decorum, a rectitude, and finally and most movingly, a capacity for pure praise that has absolutely biblical awe in it. She (and Mr. Auden, too, as it will appear) however much I may wish to take exception to the changes they have made, have provided a field day for Ph.D. candidates for years to come, who can collate versions and come up with theories about why the changes were made."

In addition to her poetry, Moore wrote a significant number of prose pieces, including reviews and essays. Many of these were collected and published as The Complete Prose of Marianne Moore. The pieces in this work cover a broad range of subjects: painting, sculpture, literature, music, fashion, herbal medicine, and sports (Moore was an avid baseball follower). Calling the collection "a civilized delight," Chicago Tribune Books contributor Larry Kart remarked that "characteristic shafts of light refract from every corner of [Moore's] universe."