Ignorance holds untapped explanatory power for environmental history, in the Arctic and beyond. I define ignorance as a state of limited knowledge, held by groups, and produced through social processes. The case study is the opening of an oil frontier in the Canadian Beaufort Sea between 1968 and 1976. Drawing from a growing body of scholarship on ignorance, as well as newly available governmental and oil industry records, I review three concepts environmental historians can use to analyse the production of ignorance. These concepts are: proprietary knowledge, selective transmission and undone research. Taken together, these concepts make visible a set of political, economic and environmental conditions that allowed ignorance to shape the approval of the first offshore drilling programme in the Canadian Beaufort Sea. Ultimately, this case study demonstrates that ignorance – like its cousins doubt or uncertainty – has been a resource that extractive industries and governmental regulators have manipulated to navigate evolving requirements of environmental planning.