In the decades around World War II, a number of abstract painters sought to “unframe” their abstractions and expand them into wall-filling murals. This dissertation analyzes moments from the history of unframed abstraction during modernism’s rise and popularity in the United States, from ca. 1935 to ca. 1960, in and around New York. Scholars have generally treated such murals as large-scale paintings rather than murals; moreover, they have located American abstraction’s growing scale firmly in the postwar years. This dissertation revises these views by examining the rich history of abstract wall painting across the 1930s, 1940s, and 1950s, and situating the murals within the architectural, social, and institutional contexts of their sites. Installed on the walls of public houses, hospitals, private homes, and office buildings, these murals raised urgent questions about art’s place in daily life, abstraction’s relationship to decoration, and collaboration between architects and painters. Using archival sources and period literature, it reconstructs the spatial and visual logic of the murals, many of which are now lost or altered. It also draws on a growing interest in reception and consumption within studies of modern American art. Arranged roughly chronologically, each chapter examines murals located in a different site type: the public institutions of the New Deal state, the pavilions of the 1939 World’s Fair, the 1940s home, and postwar commercial and civic buildings. The project situates the geometric abstractions of the American Abstract Artists within an ethos of community and social life, inculcated by the New Deal Art programs; compares painted and kinetic murals at the 1939 Fair to contemporary graphic design and exhibition display; explores Jackson Pollock’s murals within the decorative values of the upper-middle-class home; and shows how both the American Abstract Artists and the Abstract Expressionists benefitted from a boom in postwar building, which enabled the realization of ambitious murals for educational, religious, and corporate spaces. Together, the chapters offer a history of how abstraction functioned in the built environment at a time of tremendous change in American social and cultural life.