Enlightenment's Frontier is the first book to investigate the environmental roots of the Scottish Enlightenment. What was the place of the natural world in Adam Smith's famous defense of free trade? Fredrik Albritton Jonsson recovers the forgotten networks of improvers and natural historians that sought to transform the soil, plants, and climate of Scotland in the eighteenth century. The Highlands offered a vast outdoor laboratory for rival liberal and conservative views of nature and society. But when the improvement schemes foundered toward the end of the century, northern Scotland instead became a crucible for anxieties about overpopulation, resource exhaustion, and the physical limits to economic growth. In this way, the rise and fall of the Enlightenment in the Highlands sheds new light on the origins of environmentalism.