Featuring 37 objects, American Paintings, 1900--1945, the third catalog in the Gallery's Online Editions, has been launched to coincide with an important new chapter in the display of modern art at the Gallery: the inauguration of a suite of galleries devoted to American modernism in the fall of 2016. Part of a comprehensive reinstallation of the renovated and expanded East Building, the three galleries, for the first time in the institution's history, unite masterworks by the leading artists of the Henri and Stieglitz circles with related masterpieces drawn from the Gallery's rich collections of photographs and drawings. The major oils by Edward Hopper (American, 1882 - 1967), Bellows, Aaron Douglas (American, 1899 - 1979), Arthur Dove (American, 1880 - 1946), Marsden Hartley (American, 1877 - 1943), O'Keeffe, Charles Sheeler (American, 1883 - 1965), and others that will regularly be on view in the East Building are the works that are highlighted in this first release of the catalog. Among the selection are several key paintings recently acquired from the Corcoran Gallery of Art collection, including Bellows's Forty-two Kids, Hartley's Berlin Abstraction, and Hopper's Ground Swell. The detailed entries and scholarly apparatuses compiled by Robert Torchia, the catalog's primary author, are supplemented by contributions from National Gallery of Art curators and other prominent art historians. When American Paintings, 1900--1945 is completed in 2017, it will comprise approximately 100 paintings by 35 American artists who came to prominence in the United States before 1945. As online publishing continues to evolve, the catalog promises to become a dynamic tool for both scholars and the general public to actively engage with the Gallery's permanent collection and to further their understanding of early 20th-century American art.