Due to security and liability concerns, the power system research community has limited access to realistic large-scale power grid models to test and validate new operation and control methodologies. It is also difficult for industry to evaluate the relative value of competing new tools without a common platform for comparison. We designed a large-scale virtual power grid model that retains basic features and represents future trends of major U.S. electric interconnections. The designed model includes realistic power flow and dynamics information as well as a relevant geospatial distribution of assets. This model will be made widely available to the power system research community and to industry for various power system stability and control studies and can be used as a common platform for comparing the efficacies of various new technologies.