The planning of wildlife crossings requires having appropriate wildlife and spatial data and predictions of species’ interactions with the proposed structure. The spatial location of wildlife crossing structures is the most critical feature of decision-making as it determines future effectiveness of the structures. CROSPLAN (https://crosplan.wildlifecrossing.net) is a new web-based tool that provides a set of features to assist in wildlife crossing planning. The tool can jump-start projects by clipping meaningful spatial data surrounding a planned structure point. Users can drop a point on a map and access spatial data for: the predicted habitat of terrestrial species, wildlife-vehicle collisions, wildlife observations, land use/cover, noise and light models, and waterways. CROSPLAN is the primary mechanism for accessing data from the California Roadkill Observation System (CROS), which has over 255,000 roadkill observations, with an additional 18,000 “live”, “injured” and “animal sign” observations. The tool also provides predictions of various species’ likelihood of using a designed structure based on its physical characteristics and nearby landscape classifications. Scientific planning of mitigation is best informed using sufficient data. CROSPLAN utilizes over 2400 distinct spatial layers of open data at multiple scales, positioning the wildlife crossing planner to make good decisions.