Though Edith Halpert’s name may no longer resonate with many art lovers, she was in no danger of being written out of history. She merits several mentions in Aline Saarinen’s “The Proud Possessors” (1958) and quite extensive treatment in Malcolm Goldstein’s “Landscape With Figures” (2000), as well as a 1000-word entry (by Mr. Goldstein) in Oxford’s “American National Biography.” Nonetheless, Lindsay Pollock’s “The Girl With a Gallery: Edith Gregor Halpert and the Making of the Modern Art Market” (Public Affairs, 483 pages, $30) is a welcome book indeed. It tells not just the story of Edith Halpert, but illuminates a whole period in American art, a period defined in large part by Halpert’s Downtown Gallery, which was on West 13th Street between 1926 and 1940, before a series of uptown moves. (Halpert ran the gallery until her death in 1970.)

Halpert was a pioneering dealer in early modern art by living American artists, including Stuart Davis, William and Marguerite Zorach, Ben Shahn, Charles Sheeler, and Jacob Lawrence. As a result of her friendship with Alfred Stieglitz, she also became known for dealing in Georgia O’Keeffe, Marsden Hartley, Charles Demuth, and other artists. Just as importantly, Halpert was one of the first dealers in 19th-century American folk art, working with Holger Cahill and helping to build such great collections as those of Abby Aldrich Rockefeller and Electra Havemeyer Webb. (Halpert snared Mrs. Rockefeller as a client after her architect and art adviser, Duncan Candler, stumbled into the Downtown Gallery, thinking it was a front for a speakeasy.)

Edith Gregoryevna Fivoosiovitch was born in 1900 in Odessa, Ukraine. When she was 6, she moved to New York with her family. Through her teens, she worked in department stores. She took painting lessons, and she began visiting “291” and the Whitney Studio Club. One way or another, Edith Fivisovitch (as the family had simplified its name) was going to find her way in the art world. It wasn’t going to be as an artist, however: When she was 17, Edith’s instructor at the National Academy of Design, the fine painter Leon Kroll, told her she was without talent. At 18 she married Samuel Halpert, a painter she had met through the People’s Art Guild, an organization that brought art into settlement houses. Samuel had a similar Russian Jewish immigrant background. He was an important artist, knew Alfred Stieglitz, had studied in Paris and exhibited at the Salon d’Automne, and possessed a worldliness that enthralled young Edith. As Ms. Pollock writes, “If Edith wasn’t fated to achieve great heights as an artist herself, perhaps she could create that success while someone else held the paintbrush.”

In 1921 Halpert left the department store business and went to work for the investment banking firm of S.W. Straus & Co., where she remained for four years. Though she was only 20 when she went to work there, and had little formal education, she possessed a keen business sense, and styled herself an “efficiency expert.” Remarkably, she was appointed to Straus’s board. By 1925, she earned a $6,000 salary and a $10,000 bonus.

In 1925 the couple settled in Paris, where Edith met the legendary dealer Ambrose Vollard. At the same time, Sam began accusing Edith of having affairs, and the marriage crumbled. But Edith had found her calling.

“The Girl With a Gallery” features extended appearances by Stuart Davis, Arthur Dove, Juliana Force, Yasuo Kuniyoshi, Jacob Lawrence, John Marin, Georgia O’Keeffe, Abby Aldrich Rockefeller, Ben Shahn, Charles Sheeler, Alfred Stieglitz, Max Weber, and the Zorachs. It is a rich panorama, told with a pleasing briskness belying the book’s more than 450 pages. Ms. Pollock has researched her subject with formidable thoroughness, yet does not linger on minutiae. “The Girl With a Gallery” is an essential text on the New York art world of the 1920s through the 1960s, as well as a definitive account of a fascinating American woman.