Pittsburgh has been known for coal smoke since its founding. Yet no comprehensive study exists of the meaning of smoke to the city. Urban pollution is usually discussed in terms of problem and solution. Such narratives seldom do justice to the mixed losses and benefits inherent in historical outcomes or to the ambiguous motives and capacities of historical actors. This dissertation asks when, for whom, and why smoke became a problem in Pittsburgh. More broadly, it examines the rich variety of roles smoke played in urban history. Pittsburgh began as a frontier settlement. The smoky spectacle described in travelers' accounts advertised its abundant coal and industrial promise. Valued for economic potential rather than civic culture, Pittsburgh's future seemed precarious. Environmental sacrifice shored up its uncertain prospects. Nuisance judgements and local newspapers characterized opposition to smoke as a threat to economic necessity – arising from luxurious and vicious tastes of coddled and feminized elites. By the 1880s technological changes, especially the introduction of natural gas, broke connections between particular production processes and economic success. For skilled workers of Pittsburgh's National Labor Tribune, and their employers, values like cleanliness, previously regarded as antithetical to industry, became supportive of it. Natural gas made better steel, iron and glass than bituminous coal. Changes in class structure and social geography encouraged elites to reject provincialism and frontier exceptionalism. From the 1890s on, interest in economic diversification justified smoke abatement through values formerly seen as threats to economic welfare: leisure, consumption, and domesticity, embodied in real estate and retail commerce. The Mellon Institute Smoke Investigation and its successor studies (1911-1941) exhibit the interplay of such interests with changing environmental, scientific and reform orientations. Despite such sustained efforts, environmental attitudes fluctuated as depression and defense industry booms reshaped civic hopes and fears. Architects of Pittsburgh's mid-twentieth century 'Renaissance' would construct the previous 150 years as an environmental Dark Age. Yet, Pittsburghers had no more passively accepted smoke than they had unanimously resisted it. Throughout the period, smoke had been put to varied political uses, serving diverse and shifting constituencies, shaping and shaped by Pittsburgh's social and cultural history.