Abstract: The coastal shelf region influenced by the California Current system functions as a common corridor for dispersal by a diverse range of NE Pacific marine organisms with pelagic larvae. Every organism that has persisted through evolutionary time in the context of interacting with this moving, fluid coastal environment during at least a brief stage of the lifecycle has presented a successful strategy for dealing with the stresses of this current system. The accurate measurement of dispersal of many marine organisms has presented unique challenges because direct sampling of larvae or tagging of adults is often more difficult than with methods developed for terrestrial organisms. This leads to the question: how can we characterize larval dispersal within the California Current system during the present and in the past? In chapter one of this dissertation, I provide a background summary of processes which may influence dispersal for marine larvae, including an overview of the California Current system, strategies for larval duration and timing of release, ecological processes of competition and demography, and larval behavior. Additionally, I review previous research results revealing spatial and temporal patterns among populations resulting from dispersal. Two species of estuary crabs were selected as model organisms for addressing the question of interest via genetic methods because they occur in clearly defined habitat patches, and have a moderate larval duration. Rhithropanopeus harrisii, was introduced in the early part of the century, and occupies a very similar ecological niche in the Atlantic, is addressed in chapter 2. Hemigrapsus oregonensis, the subject of a genetic study presented in chapter 3, is a native shorecrab with a range stretching from lower latitude Alaska to Mexico. Both of these crabs were sampled, and the mitochondrial cytochrome oxidase subunit I gene was sequenced in order to create a phylogenetic network, and to estimate approximate rates of dispersal and interpret phylogeographic history. Finally, presented in chapter 4, is a spatial statistical model developed to describe the level of connectivity, or ease of dispersal within the coastal corridor, experienced from the perspective of these invertebrate species. This model was designed with a statistical approach that could be adapted for use with other species, using inputs of data from interpolated pressure-field current vectors, and genetic dispersal estimates.