The Tree-Ring Laboratory (TRL) was established in 1979 and concentrates on the development of exactly-dated annual ring-width chronologies from ancient forests worldwide. Tree-ring chronologies provide unique archives of environmental history and have many inter-disciplinary applications. These tree-ring chronologies are based on small core samples extracted non-destructively from living trees and cross-sections cut from dead logs. We specialize in the reconstruction of past climate and stream flow, the socioeconomic impacts of past climatic extremes, the dating of historic structures, and the identification and mapping of ancient forests. We conduct research in the southeastern United States, the southern Great Plains, California, Mexico, and Brazil. The TRL is active in the conservation of ancient forests and has assisted the preservation of old growth remnants in the cypress-tupelo forests of the South, the oak-hickory forests of the central United States, the blue oak and conifer woodlands of California, and the conifer forests of Mexico. The TRL helped establish the Ancient Cross Timbers Consortium which unites universities, federal and state agencies, conservation organizations, and private landowners for research, education, and conservation efforts in these widespread ancient forest remnants still found on the margins of the southern Great Plains.