Due to the size of this book, we had to make into 2 Books. This is Part 1This report was prepared by the U.S. Environmental Protection Agency's (EPA's) Air, Climate, and Energy (ACE) research program, located within the Office of Research and Development, with support from the Cadmus Group. The ACE research program provides scientific information and tools to support EPA's strategic goal of taking action on climate change in a sustainable manner. Such action includes both mitigation, which involves reductions in the movement of heat-trapping greenhouse gases into the atmosphere, and adaptation, which involves preparing for and adjusting to the expected future climate. Both are important, but this report focuses on adaptation to climate change. Climate change impacts are diverse, long-term, and not easy to predict. Adapting to climate change is difficult because it requires making context-specific and forward-looking decisions regarding a variety of climate change impacts and vulnerabilities when the future is highly uncertain. Cities are on the front line for responding to potential climate change impacts, but often do not know precisely the qualities or characteristics that make them vulnerable or resilient to different impacts. This report supports the goal of taking action on climate change in a sustainable manner by developing a conceptual framework of urban resilience to climate change and using rigorously selected indicators to assess community resilience to climate change. This framework is then successfully applied to two different communities (Washington, DC and Worcester, MA) to evaluate their levels of resilience to climate change. Results support the usefulness of this indicator-based approach in identifying traits that enhance or inhibit each community's resilience to focus adaptation planning on issues and areas that are least resilient to climate change impacts.