An original component of the 1811 grid plan for New York City, Union Square has acquired an association as a place in which the ideals of American republicanism and democracy are both signified and enacted. The square is occupied by a central lawn, a series of statues, a small building to the north, and an open plaza set aside as a place for public meetings. Using the concept of “urban semiology” described by Roland Barthes, this paper is concerned with two things: the ways in which the signifying function of the square has been attributed variously to the statues and to the open space of the plaza; and the ways in which the signifying elements were first created, then altered and appropriated by different urban actors at different times over the past two centuries. Exploring the question of agency, of the mechanisms through which signification is achieved, the focus will be on the ways in which the statues and the open space of the plaza have served as symbols, icons, and indexes of political ideas. Concluding with the early Cold War period, when the symbolic expression of global politics across all forms of culture from media, to the arts, to architecture and city planning, was at its bluntest and least nuanced, the paper will discuss the nineteenth and early twentieth century history of the square in order to understand how and why the use and meaning of Union Square continues to be so contentious.