The Nature Conservancy's Priority Conservation Areas and Targets can be viewed through their interactive map viewer or downloaded as a shapefile (select the download button in the upper right corner of the interactive map viewer).
Description of data from http://uspriorityareas.tnc.org/: "The Nature Conservancy has been a leader in spatial conservation planning for many years. The primary planning tool used by the Conservancy for landscape-scale conservation planning over the past decade has been Ecoregional Assessments. Our United States Ecoregional Assessments identify priority areas for conservation within the United States. This includes data from 67 Ecoregional Assessments, which identified over 9,000 conservation priority areas. Importantly, this dataset contains the conservation targets that we hope to conserve within these priority areas. Conservation targets include both species and habitat types (e.g. plant communities; ecosystems). Our dataset includes 8,507 unique species and 6,633 habitat types. Across the United States a common naming system was used for our species targets. In contrast, names for habitat targets may be specific to each ecoregion. Additional information about each ecoregional assessment, including vintage, stakeholder participation, and other methodology, is available at http://east.tnc.org. For more information about The Nature Conservancy’s U.S. Priority Area data contact Joe Fargione (jfargione@tnc.org). Use of the information is subject to the Terms of Use: http://www.nature.org/about-us/governance/terms-of-use.xml?src=f9."