The dataset includes Hendy test of speleothem carbon isotopes and oxygen isotopes, used to reconstruct climate in southeastern Alaska during the past ~3,500 years. Speleothem WB-21-5-A was collected in Wishbone Cave (55.774 N, -133.191 E; 420 m.a.s.l.) and speleothem WA-21-6-A was collected in Walkabout Cave (55.776° N, 133.195° W; 350 m.a.s.l.) on May 21, 2022 and June 21, 2022, respectfully. The data collection was completed between September 2021-March 2022. Stable isotopes were measured on a ThermoFisher Delta V isotope ratio mass spectrometer.