Further research into the cross-sector dependencies of critical infrastructure sectors and the cascading effects of a breach to any of these sectors is necessary to ensure the country’s critical infrastructure, and this research demands cross-sector collaboration and information sharing at nearly all levels. This meeting explored the state of critical infrastructure security in the United States and identified R&D priorities; methods of modeling and assessing vulnerabilities in critical infrastructure security to prevent breaches or minimize cascading effects; how communication across sectors and public-private partnerships can enhance critical infrastructure security, and how pending legislation impacts physical and cyber infrastructure security.