The eastern margin of North America has been affected by a range of fundamental tectonic processes in the geologic past. Major events include the Paleozoic Appalachian orogeny, which culminated in the formation of the supercontinent Pangea, and the breakup of Pangea during the Mesozoic. The southern New England Appalachians exhibit a particularly rich set of geologic and tectonic structures that reflect multiple episodes of subduction and terrane accretion, as well as subsequent continental breakup. It remains poorly known, however, to what extent structures at depth in the crust and lithospheric mantle reflect these processes, and how they relate to the geological architecture at the surface. The Seismic Experiment for Imaging Structure beneath Connecticut (SEISConn) was a deployment of 15 broadband seismometers in a dense linear array across northern Connecticut. The array traversed a number of major tectonic boundaries, sampling across the Laurentian margin in its western portion to the Avalonian terrane at its eastern end. It also crossed the Hartford rift basin in the central portion of the state. The SEISConn stations operated between 2015 and 2019; data from the experiment are archived at the Incorporated Research Institutions for Seismology Data Management Center and will be publicly available beginning in 2021. A suite of imaging techniques is being applied to SEISConn data, with the goal of providing a detailed view of the crust and mantle lithosphere (including discontinuities, seismic velocities, and seismic anisotropy) beneath the southern New England Appalachians. Results from these analyses will inform a host of fundamental scientific questions about the structural evolution of orogens, the processes involved in continental rifting, and the nature of crustal and mantle lithospheric deformation during subduction, terrane accretion, and continental breakup.