This article explores how Grand Central Terminal organized and "aestheticized" the metropolitan crowd. Through a combined analysis that integrates architectural form and social discourse, the article examines the dynamic relationships between changes in the mythologies of the crowd and changes in the series of Grand Central stations that occupied the same site in midtown Manhattan between 1871 and 1914. At the first station, Grand Central Depot, extreme overcrowding grew in proportion to the increase in traffic flow and in the railroads' operational efficiency. At the turn of the century, the architecture of passenger movement became the object of intense design and construction activity in which passenger spaces became both more carefully organized and more monumental. As the culmination of these changes, the 1914 terminal represented the city and its crowds in an idealized microcosm and the passengers as a collective monument to the railroad empire. Within this new monument, the concourses and ramps engineered human movement according to a paradigm of mechanized rationality. This article demonstrates that the aesthetics of passenger circulation at Grand Central Terminal participated in a larger culture of technological domination and rationalized sociability. Each section describes a progressive step in the incorporation of the crowd by the mechanized apparatus of the railroads, and different discourses of the crowd are linked to corresponding spatial forms in Grand Central. This view of Grand Central Terminal, a beaux arts building, raises significant historiographic questions as to traditional distinctions between modernism and nineteenth-century historicism.