Measurements of near-surface salinity and temperature were made over a period of 16 months in the Connecticut River estuary, and estuary basically of the salt wedge type. The temperature distribution was found to be very highly correlated with the salinity distribution. The horizontal salinity distribution occurred primarily in two modes, a riverine mode and a plume mode, corresponding to salinity transitions mostly within the river itself and to those mostly within Long Island Sound. Similarity variables are developed for each of the two distribution modes which render the data in compact forms that should have applications to other estuaries of a similar type.