This data release includes 40Ar/39Ar data from the U.S. Geological Survey for samples from Old Mine Park Area, Trumbull, Connecticut. Mineral samples were collected by Robert Wintsch and Harold Moritz. Potassium-bearing mineral grains were separated from the bulk sample and analyzed by argon geochronology at the U.S. Geological Survey Bascom ARgon Dating (BARD) Laboratory in Reston, Virginia. The data provide age constraints on units in the relevant geologic mapping area.