These datasets provide spatially-explicit estimates of the magnitude of giant sequoia foliage dieback along selected trail corridors in Sequoia and Kings Canyon national parks, California, from 2014 through 2017. They additionally provide giant sequoia tree-ring measurements, through the year 1989, for two locations in the Giant Forest grove, Sequoia National Park, California. These data support the following publications: Nathan L. Stephenson, Adrian J. Das, Nicholas J. Ampersee, Kathleen G. Cahill, Anthony C. Caprio, John E. Sanders, A. Park Williams, Patterns and correlates of giant sequoia foliage dieback during California’s 2012–2016 hotter drought, Forest Ecology and Management, Available online 7 November 2017, ISSN 0378-1127, https://doi.org/10.1016/j.foreco.2017.10.053. Martin, R. E., G. P. Asner, E. Francis, A. Ambrose, W. Baxter, A. J. Das, N. R. Vaughn, T. Paz-Kagan, T. Dawson, K. Nydick, and N. L. Stephenson. Submitted. Remote measurement of canopy water content in giant sequoias (Sequoiadendron giganteum) during drought. Submitted to special section in Forest Ecology and Management.