In late nineteenth- and early twentieth-century New York City, open spaces became as significant as built forms. Scholarship on the rapidly growing city and images of it has often emphasized superlatively tall skyscrapers, vast infrastructure projects, and the density of buildings and people. My dissertation offers a reoriented perspective on these urban transformations by addressing the spatial inverse of the skyscraper and the crowd: the open spaces between buildings and the salutary light and air that they preserved. Forged through legal battles over property and contoured by everyday use, these interstices were integral components of artists’ and residents’ intersecting experiences of the city—especially for women, immigrants, and African Americans, who disproportionately lived and labored in dense places. Yet, the relative invisibility of these “negative spaces” challenged traditional modes of visual representation, such as cartographic views, architectural rendering, and landscape painting. Artworks by John Sloan, Georgia O’Keeffe, and Aaron Douglas, reveal that painters turned to open-air zones to explore the new spatial dimensions that knit the city together, and that they exploited modernism’s freedoms in form, style, and subject matter to do so. Through maps, municipal records, and artists’ archives, three thematic case studies resituate art objects within the places of their making and spatialize artists’ biographies. By examining how artists’ strategies to negotiate space in their paintings were intertwined with the efforts of city planners and other civic stakeholders to shape urban open space, my project engages and critiques a historical narrative in which twentieth-century art inevitably culminates in abstraction—and argues for the importance of specificity of place and space in art historical analysis.