Wildlife crossing structures are a common strategy for reducing barrier effects of roads and improving population and landscape connectivity. The extent of disruption in ecological and genetic connectivity caused by roads varies among taxa, as does the success of various crossing structure types in mitigating the reduced connectivity. While most earlier studies of crossing structures focused on large-bodied, high-mobility species, a larger diversity of taxa is now being evaluated. We have been monitoring small mammal populations in the Interstate 90 Snoqualmie Pass East Project (SPEP) in Washington State from pre-construction through post-construction phases of multiple wildlife crossing structures. Objectives are to document species presence, relative abundance, habitat and microhabitat use, and population genetic structuring, with the goals of assessing the effectiveness of crossing structures and providing recommendations for the adaptive process of adjusting structures and their associated habitat restorations. We conducted occupancy surveys for American Pikas at natural talus sites and anthropogenic rock habitats 2009-2018. Between 2013 and 2018, we live-trapped small mammals on 6 paired grids (one of each pair north of the highway and one south) in forest near finished or planned crossing structures. Several grids were surveyed each year, typically for one trapping session of two consecutive nights. We identified each captured animal to species; recorded standard measurements, body mass, sex, and age; took a genetic tissue sample (small ear or tail clip); and marked animals with temporary nail polish or permanent PIT tags. On a subset of grids, we measured habitat and microhabitat features near each trap station. Pika occupancy was relatively high over the project area, but somewhat lower in anthropogenic sites than natural sites. Pikas colonized some new rock patches within 2-4 years of their construction. Species richness and relative abundances of the other small mammal species varied across sites and years, but with some regularity of the dominant species (Peromyscus maniculatus and P. keeni). Four years after the first wildlife undercrossing of the SPEP was completed, and two years after habitat restoration, we captured four of the nine species/species groups captured in reference forest sites; most were habitat generalists. One year later in 2018, we captured one additional species, a forest specialist. Additionally, most captures in the crossing structure and adjacent restorations sites were near snags, logs, and rock and brush piles that had been placed as habitat features. Notably, for many of these small mammals, their small home ranges and limited dispersal capacity compared to large mammals means that the crossing structures are not just a pathway for movement between areas, but also serve as territories and reproductive sites. Multiple generations may be required to connect populations across the highway.