In this paper we present a data set that is intended to support ongoing research to address the increasing dependence of electric power networks on natural gas pipelines. Several efforts have emerged to expand the set of sample networks for studying electric power systems at scale, which can be used to develop and test control and optimization concepts and algorithms for these systems. Comparable efforts have developed gas-network test instances that have been valuable for advancing parallel efforts. However, available data sets with realistic representations of these two types of infrastructure systems have not represented their coupling. Here we aim to address this model development shortfall by providing a combined gas-electric test instance, developed from open sources, that represents pipeline and power grid systems in the U.S. with specific information about how these networks interact. Based on our understanding of the function of pipeline systems, we develop a model of a regional system based on publicly available data, and connect it to the ACTIVS U.S. synthetic power grid case. The outcome is a basis for meaningful studies of the interaction between the two types of systems, and exploration of novel management approaches.