Characterizing patterns of genetic diversity including evidence of local adaptation is relevant for predicting and managing species recovering from over-exploitation in the face of climate change. Red abalone (Haliotis rufescens) is a species of conservation concern due to recent declines from over-harvesting, disease, and climate change, resulting in the closure of commercial and recreational fisheries. We hypothesized that the environmental mosaic that defines nearshore habitats in the California current ecosystem, including variable pH and temperature, has enriched some regions for locally-adapted genotypes that may be important for species persistence in changing environments. Using whole genome re-sequencing data from 23 populations spanning their entire range (southern Oregon, USA, to Baja California, MEX) we investigated population connectivity and local adaptation to inform management strategies. We discovered high genetic diversity that is shared within and among populations, suggesting high historical range-wide gene flow. Using multiple layers of environmental metadata, we tested for genotype-environment associations that would reveal local adaptation. We found little evidence for large selective sweeps between populations that occupy local habitats that vary by pH, strength of upwelling, chlorophyll, salinity, and sea surface temperature. While related physiological studies reveal evidence of local adaptation to pH in red abalone, our data suggest that the underlying genetic architecture may be polygenic and therefore difficult to detect from traditional genome scans. Overall, red abalone harbor a massive reservoir of genetic diversity that may be important for future adaptation, but adaptive recovery may be limited by current demographic decline. Given the high genetic connectivity across their range, state-mandated regulatory actions would be most effective if aligned across jurisdictional boundaries (i.e., Mexico, California, and Oregon).