Kootz also exhibited work by Georges Braque, Fernand Léger, James Brooks, Giorgio Cavallon, Arshile Gorky, David Hare, Hans Hofmann, Ibram Lassaw, Herbert Ferber, Raymond Parker, William Ronald, Tony Rosenthal, Conrad Marca-Relli, Georges Mathieu, Emil Schumacher, Pierre Soulages, Kumi Sugaï, Zao Wou Ki, and others.
[5] Between 1919 and 1921 he became acquainted with progressive artists, including Peter Blume, Charles Demuth, Preston Dickinson, Carl Holty, Yasuo Kuniyoshi, John Marin, and Max Weber.
[8] Beginning in 1930 and continuing into the 1940s with books, articles, forceful letters to the New York Times and other activities, Kootz urged artists to sever their dependence on Europe, to drop the search for typically “American” art, and to find original, gutsy forms of expression.
His first book, Modern American Painters (1930) offers critiques of Blume, Demuth, Dickinson, Arthur Dove, Kuniyoshi, Marin, Georgia O'Keeffe, Charles Sheeler, Maurice Sterne, Max Weber, and brief descriptions of seven others, including Walt Kuhn and Niles Spencer.
"[6] To show that his would be "an international gallery interested in quality," Kootz began with an exhibition of Fernand Léger, held in temporary quarters, in April 1945.
Highlights of this era include: Following a "real upsurge of buying American painting" that had begun in the fall of 1955,[5] the gallery moved to larger quarters at 1018 Madison Avenue in September 1956.
The Gallery's opening exhibitions featured Pierre Soulages, Georges Mathieu and Hans Hofmann, as well as "Art for Two Synagogues" with sculptures by Ferber & Lassaw.