Frank K. M. Rehn (1886-1956), son of the marine painter Frank Knox Morton Rehn, after several years' experience as an employee of the Milch Galleries and as exhibition manager for the Salmagundi Club, opened his own art gallery in 1918. In its earliest years, the gallery operated as the Galleries of Frank K. M. Rehn. From the mid 1920s through the mid 1940s, the name used was Frank K. M. Rehn Galleries. As early as 1946, the gallery was referred to simply as Rehn Galleries. The gallery closed in 1981.
Throughout its existence, Rehn Galleries specialized in representing American painters. During the first five years Rehn's operation was a private gallery at 6 West 50th Street, New York City. Among the artists he first represented were older, established men such as J. Alden Weir, George Inness, Alexander Wyant, Theodore Robinson, Thomas Dewing, and John H. Twachtman. Occasionally, Rehn handled works by such luminaries of the period as Robert Henri, George Luks, and John Singer Sargent. Among the living artists affiliated with the gallery in its first years were Daniel Garber, Walter Griffin, Dodge MacKnight, and Robert Spencer. Rehn's most popular artist during this time was Childe Hassam, who sued for recovery of a painting that, although acquired by Rehn through a reputable dealer, had been stolen from Hassam's studio many years earlier.
Despite the newspaper publicity surrounding Hassam's lawsuit, the business was a successful venture almost immediately. Very early, a number of important collectors including Duncan Phillips, John Gellatly, John T. Spaulding, Albert McVitty, E. W. Root, and C. Vanderbilt Barton displayed confidence in Rehn's judgment and integrity, which enhanced his gallery's reputation and stature among both collectors and artists. In 1923, the gallery moved to 693 Fifth Avenue and began operating as Rehn Galleries, a commercial gallery in the same building that housed in a building that housed Kennedy and Company and the Bourgeois Galleries. At this time, Rehn hired an assistant, John C. Clancy (1897-1981), who had formerly been with Henry Reinhardt and Son and M. Knoedler.
The Rehn Galleries soon enjoyed a regular following among museum curators and collectors visiting from out of town. The gallery's roster of artists grew along with its reputation. Rehn focused almost exclusively on American painters, occasionally showing drawings and prints by artists who were primarily painters; notable exceptions were sculptor Mahonri Young and Henry Varnum Poor who, in addition to being a painter, was known for his work in ceramics. Among the painters eventually represented were: Peggy Bacon, George Bellows, Alexander Brook, Charles Burchfield, John F. Carlson, John Carroll, Howard Cook, Jon Corbino, Virginia Cuthbert, Andrew Dasberg, Sidney Gross, Edward Hopper, Alexander James, Irving Kaufmann, Yeffe Kimball, Leon Kroll, Peppino Mangravite, Reginald and Felicia Meyer Marsh, Henry Mattson, Henry Lee McFee, Kenneth Hayes Miller, Charles Rosen, Robert Riggs, Alexander Russo, Elizabeth Sparhawk-Jones, Eugene Speicher, Henry Strater, Richard Derby Tucker, Franklin C. Watkins, and Denny Winters.
In 1930, Rehn Galleries moved one block south to the Air France Building at 683 Fifth Avenue, remaining there for thirty years. John C. Clancy, Rehn's long-time assistant, became Gallery Director in 1953 after a stroke prevented Rehn from continuing to run his business in an active capacity. Eventually, Rehn's widow sold Clancy the gallery, which he continued to operate under varying names, including Rehn Gallery, Frank K. M. Rehn Galleries, Frank Rehn Gallery, and Rehn Galleries. From 1960 until 1966, The Rehn Galleries were at 36 East 61st Street from 1960 until 1966, when the gallery moved to a space formerly occupied by Kootz Gallery at 855 Madison Avenue, where it remained in business for another fifteen years.