The average size of container vessels calling at U.S. ports has grown considerably over the past five years, and the trend is expected to continue. As U.S. ports prepare to welcome ever-larger mega vessels, this paper assesses the effects that these and related alliance may have on port authorities, the role of the port authority and the fiscal and political factors to be considered. It provides a useful tool to help policymakers and executives at U.S. port authorities, large and small, understand their role as they position their ports to benefit from the changing landscape in the maritime shipping industry.