This paper explores the changing role of the public library, and determines its impacts on communities and cities. It also examines the relationship between libraries and planning policies, and the extend to which they inform the success of public libraries. The analysis centres on the design of modern public libraries, and the community and economic contributions they provide. Through analyses of the Vancouver Public Library, the Seattle Public Library, and the Toronto Public Library, it is evident that public libraries provide significant contributions within the communities they serve. Well-designed library buildings provide an important public space, and provide people with access to information and technology needed to participate in the knowledge economy, in turn producing significant economic gains for the city. This research finds that planning policy alone is unable to ensure the success of a city`s public library system. Support from the public and municipal leaders, combined with strong policy directives, is needed for a city`s public library system to succeed.