The Plains CO2 Reduction (PCOR) Partnership is one of seven Regional Carbon Sequestration Partnerships (RCSPs) competitively awarded by the U.S. Department of Energy (DOE) National Energy Technology Laboratory in 2003 as part of a national plan to mitigate greenhouse gas emissions. The PCOR Partnership is led by the Energy & Environmental Research Center at the University of North Dakota in Grand Forks, North Dakota, and includes more than 80 stakeholders from the public and private sector. The PCOR Partnership region includes all or parts of nine U.S. states and four Canadian provinces. Phase II, the validation phase, was an extension of the characterization phase (Phase I, 2003?2005) of the program and covered the period from 2005 through 2009. Phase II activities focused on carbon storage field validation projects that were designed to develop the local technical expertise and experience needed to facilitate future large-scale carbon dioxide storage efforts in the region?s subsurface and terrestrial settings. These activities included four field validation tests (three geologic and one terrestrial) along with continued refinement of the regional characterization of sequestration opportunities, elucidation and clarification of the regulatory and permitting requirements for sequestration as well as the identification of commercially available carbon dioxide capture technologies, integration of the regional efforts with the other DOE RCSPs, and continuation of local and regional public outreach initiatives. Results of the Phase II activities indicated that the PCOR Partnership region has tremendous opportunities for carbon sequestration in geologic and terrestrial settings. Total funding for Phase II exceeded $29 million, with 56% of that funding provided by DOE and the balance contributed by industry and other nonfederal partners. This report documents and summarizes all work performed over the course of the Phase II effort and presents the findings, recommendations, and conclusions of this work.