In this seminar we begin with a central insight of environmental history, the premise that "nature" - meaning the beyond-human world of plants, animals, soils, waters, microbes, insects, climate, and so on has actively shaped human history. We thus frame "environment" as historical actor rather than passive backdrop to human activity. This approach forces us to think transnationally, though our geographic focus is North America and specifically the United States. It also requires interdisciplinary thinking, pressing against the "humanist" boundaries of traditional history. Human ideas about "nature" are central to our work, and we will explore how those ideas have changed and continue to change, and with what consequences. Finally, we prepare ourselves to contribute our own insights and research findings to the still-emerging field of environmental history.