Until recently, the reported range of Spisula solidissima similis , known as the “southern” surfclam or Raveneli’s surfclam , extended from the Gulf of Mexico to Cape Hatteras. Recent documentation shows S. s. similis far north of its prescribed range: in Long Island Sound New York and Massachusetts (New England hereafter), including populations of S. s. similis which co-occur with its morphologically cryptic and commercially harvested sister taxon S. s. solidissima . With no reports of geographically intermediate populations between the Cape Hatteras and New England populations, it is unclear if the New England populations were initiated by contemporary, possibly anthropogenic, founding events or if the “southern” surfclam has been present but undetected in this expanded range historically. This talk will address population structure analyses using genomic data from 130+ S. s. similis samples from Georgia and New England , using S. s. solidissima as an outgroup. This analysis allows for the comparison of population connectivity and genetic diversity among the New England sites and between them and Georgia. Patterns of DNA sequence variation will be used to infer the demographic history of New England populations and whether there is ongoing gene flow across the Atlantic coastal population gap . With interest growing in surfclam aquaculture, understanding population relationships and the distribution of genetic diversity in this species can help plan surfclam breeding strategies.