This data release includes electron microprobe and 40Ar/39Ar measurements collected at the U.S. Geological Survey for samples from the East Derby Shear Zone (EDSZ) in Connecticut, USA. Rock samples were collected by Bryan Wathen, now at the University of Wisconsin. Muscovite, biotite, chlorite, plagioclase, and K-feldspar were analyzed by electron probe microanalysis at the U.S. Geological Survey, Reston Electron Microbeam Laboratory. Aliquots of muscovite from several samples were analyzed by argon geochronology at the U.S. Geological Survey Bascom ARgon Dating (BARD) Laboratory in Reston, Virginia. The 40Ar/39Ar data constrain the cooling history of the rocks around the EDSZ as well as the time(s) of deformation in the EDSZ.