In 1994 Congress passed the National Space Transportation Policy (NTSP) that called on the National Aeronautics and Space Administration (NASA) to pursue the development of government and private sector partnerships, and to create private commercial spaceport and launch facilities capable of supporting affordable and sustainable space exploration. Since the passage of the NTSP, NASA has sought to develop collaborative public/private partnerships and foster new intergovernmental relationships for the development of technologically advanced space vehicles and the creation of a commercially based space transportation system. The loss of the Columbia and the lack of viable replacement in the near-term for the shuttle have emphasized the lack of a realistic long-term policy vision for America to create a viable and cost effective space transportation system. Given the current competition for space program funding with national security concerns, it is important that future space program policy possess a clear understanding of how sustainable transportation systems have traditionally evolved in America. This paper examines public/private relationships and how past intergovernmental interdependencies have impacted the development of canal, railroad and aviation transportation systems within the United States. The goal of this paper is to identify transportation models that NASA may use in the development of a national space transportation system. Growth of transportation systems can be best viewed as an incremental process fueled by economic demand and support of national security and shaped by both the geography of the United States and the advancement of transportation technology. The role of government and its relationship with private enterprise in development of American transportation systems has been varied and often complex. Study of canal, railroad and aviation systems reveals that development of individual transportation systems was most often undertaken by private enterprise and local and state governments. Sustainability of these systems has become increasingly dependent on federal government sponsorship, funding and regulation. Financing methods for transportation systems has also been extremely varied. These strategies included public improvement bonds, loans, and issuance of stocks, barter arrangements, earmarked state revenues, debt, and tolls. States and federal government have also levied taxes on tickets, cargo, fuel, and on transportation companies. In times of emergency, transportation systems have also benefited from extensive federal financial assistance and protective legislative to safeguard national commerce and security. Private ownership and operation of transportation modes, canals, railroads and airline companies, and/or operation of key transportation nodes, such as airports, by local governments are clearly preferred by both citizens and legislators. Each major system has relied on extensive involvement of both the public and private sectors. These respective roles have differed by system and have changed to some extent over time. Transportation systems typically developed in a fragmented, incremental manner. Thus, we have historically not had consistent national policies related to transportation. The federal government, however, almost exclusively developed space transportation. Because of this, widespread involvement by commercial actors,