The United States's National Spatial Data Infrastructure (NSDI) model presumes that the local government agencies of counties and municipalities will share their geographic information freely with government agencies of regions, states and federal agencies. This article takes up the issue of local government involvement in the NSDI by asking the question: why should local governments involve themselves in the NSDI? This question is informed by considering the social and technological imbrication of the NSDI. One of the oldest spatial data infrastructure projects, the NSDI offers insights into the complexity of implementing infrastructure in federal models of shared governance. This article focuses on the political and financial dimensions of developing infrastructure among local governments. Trust is quintessential at this level of government. Local government agency activities experience an inherently closer coupling with political representatives and with different agencies in both intramunicipal and intermunicipal activities. Building the NSDI is fundamentally an interagency act and thus a matter of trust. Trust is a key issue in the development of the NSDI, as the results of a study of Kentucky local government agencies indicate.