Wildlife crossing structures (WCS) are proposed as the primary way to improve wildlife connectivity across transportation. Barrier fencing is used independently to reduce wildlife-vehicle collisions (WVC). WCS effectiveness depends on understanding the interacting influences of wildlife and human activity. There are no published, science-based, and objective methods for decision-support for WCS siting at US state extents. To inform WCS planning on 8 highways throughout CA, supported by ~$28 million from the Wildlife Conservation Board, locations were identified: 1) where new over OR under-crossings are ecologically needed and feasible to construct, and 2) where existing structures provide connectivity. The following spatial datasets were used: 1) available wildlife occurrences and movement, 2) WVC, 3) habitat suitability models, 4) topography, 5) human disturbance and development, 6) ownership, and 7) infrastructure data. I developed a logic-based model in GIS to associate the disparate data types in a decision-support framework. The result was identification of places along each highway of types of actions critical to reduce wildlife-vehicle conflict and improve connectivity. For each highway, one to three locations are being or have been evaluated by engineers and plans developed for construction of 13 WCS and fence alignments, with an eventual cost of over $200 million.