Regional experts, TNC and NatureServe ecologists worked with spatial data and analyses of the distribution and condition of targeted species and representative ecosystems within the Upper Mississippi River Basin to identify a set of areas of biodiversity significance. The areas they identified represent the full array of places that harbor the best remaining examples of the ecological systems that contain the best examples of rare and imperiled, common and representative species, communities, and the ecological processes that sustain them in a connected manner to provide for directional flow and important environmental and ecological processes.