Abstract: East-West Gateway partnered with the Missouri Resource Assessment Partnership to develop a Regional Ecological Framework as a tool to link conservation, mitigation, and transport planning. Ecological significance is one outcome of that framework, which will be used in the update of the region's Long Range Transportation Plan. Federal transportation planning requirements, as outlined in SAFETEA-LU, now require that development of Long Range Transportation Plans include consultation and cooperation among local/state agencies that monitor land use management, natural resource preservation, and historic preservation. Plans are also required to include a discussion of environmental mitigation activities. This Ecological Significance data will be used to develop environmental mitigation strategies for the region. Ecological Significance is a ranking of patches of land to illustrate their relative value within the ecosystem of the St. Louis region. Higher numbers = higher significance. This file has been dissolved and then split by county boundaries. Please refer to the report "Ecological Approach to Infrastructure Development" for methodology details.