The dataset consists of morphology (length: width, length: height and surface area: volume ratios), density (bulk density, micro density and apparent porosity) and shell thickness (average thickness, maximum thickness and percentage calcite) of Mussel (Mytilus edulis) shells from the north Atlantic. Mussel shells were collected from Nahant Bay, Massachusetts; Vineyard Sound, Massachusetts; Long Island Sound, New York and New York harbor. Shells cover a range of time periods; the early 1900s, the early 1960s and 2021-2023. The historical material was stored in marine invertebrate collections at the American Museum of Natural History. The dataset was collected to assess long term climate change impacts on mussel shell shape, thickness and density along the east coast of the United States. To collect morphology data, digital calipers and 3D CT scans were used, while a modified buoyant weight method was used to collect density measurements. Shells were embedded in epoxy resin to expose the internal shell. Shell thickness was measured using light microscopy images of embedded shells.