The U.S. Geological Survey, in cooperation with the North Carolina Turnpike Authority, conducted a study to establish baseline water-quality conditions and bed-sediment chemistry in Currituck Sound, North Carolina, prior to construction of the Mid-Currituck Bridge. This Data Release contains the associated data described in the Open-File Report, “Characterization of Water-Quality and Bed-Sediment Conditions in Currituck Sound, North Carolina, Prior to the Mid-Currituck Bridge Construction, 2011-18”. These datasets contain information on analytical constituents measured in samples, surface-water environmental and quality-assurance sample results, bed-sediment environmental and quality-assurance sample results, phytoplankton taxonomy data, and water-velocity measurement results. Data were collected from August 2011 to January 2018 at five sites distributed along the planned alignment of the Mid-Currituck Bridge in Currituck Sound, North Carolina.