Interstate 5 (I-5) is a high-traffic highway that potentially acts as a continental barrier to wildlife. We propose the definition that “a continental barrier is any divide across a continent that restricts wildlife movement and creates habitat connectivity issues and/or behavioral changes across ecoregions along its length”. We conducted a meta-analysis of literature using an observed (in literature) to expected (from habitat suitability models) ratio. We divided I-5 into seven ecoregions and used habitat maps to create lists of ‘ecologically expected’ (EE) native mammalian species for each region. Using Google Scholar, we collected literature that addresses the effects of I-5 on any regional EE species (OI-5), or any regional species interactions with highways (OA). Ungulates had the highest OI-5/EE and OA/EE ratios (0.7 and 0.78), while soricomorphs had the lowest (0.09 and 0.2). For all species, Klamath-Siskiyou Mountains had the highest OI-5/EE ratio (0.58) and Southwestern WA had the highest OA/EE ratio (0.73), while Northwestern WA had the lowest (0.12 and 0.2). Of the 116 pieces of literature collected, analysis thus far shows 82% support I-5 being a continental barrier for a limited subset of EE species.