ABSTRACT: This article traces the origins of conservationist thinking among a group of scientists who constructed a system of American natural history while exploring the transappalachian frontier between 1730 and 1830.Despite the importance of conservationist thought in American environmental history, we know too little about how its major precepts--balance, interrelatedness, and the practical and spiritual importance of nature--were formulated prior to the Darwinian era. The early conservationists deserve more attention because they provided a firm foundation for ideas that took shape and triumphed in the second half of the nineteenth century.