Responding to the challenges of fostering regional growth and employment in an increasingly competitive global economy, many U.S. states and regions have developed programs to attract and grow companies as well as attract the talent and resources necessary to develop innovation clusters. These state and regionally based initiatives have a broad range of goals and increasingly include significant resources, often with a sectoral focus and often in partnership with foundations and universities. These are being joined by recent initiatives to coordinate and concentrate investments from a variety of federal agencies that provide significant resources to develop regional centers of innovation, business incubators, and other strategies to encourage entrepreneurship and high-tech development. This has led to renewed interest in understanding the nature of innovation clusters and public policies associated with successful cluster development. The Board on Science, Technology, and Economic Policy (STEP), conducted a symposium which brought together state and federal government officials, leading analysts, congressional staff, and other stakeholders to explore the role of clusters in promoting economic growth, the government's role in stimulating clusters, and the role of universities and foundations in their development. Growing Innovation Clusters for American Prosperity captures the presentations and discussions of the 2009 STEP symposium on innovation clusters. It includes an overview highlighting key issues raised at the meeting and a summary of the meeting's presentations. This report has been prepared by the workshop rapporteur as a factual summary of what occurred at the workshop.