As a researcher in the United States Geological Survey, she aided in uncovering records of plant life from the Miocene around the Eniwetok and Bikini Atolls in the southern Pacific Ocean and from the Cenozoic era in the Rocky Mountains.
Leopold's work as a conservationist included taking legal action to help save the Florissant Fossil Beds in Colorado, and fighting pollution.
Her research involved extracting pollen and spores from ancient rocks and sediments and comparing this evidence of fossil plants with those of modern specimens in order to infer what past landscapes and environments were like.
[7] Her work also included studying drilled cores containing pollen from the Miocene Epoch that revealed evidence of a tropical rainforest in the Eniwetok and Bikini Atoll area of the Pacific Ocean (now the Marshall Islands).
[3] By studying plant fossil records from the Rocky Mountains in Colorado, Idaho, and Wyoming, Leopold provided inferences about the paleoenvironment of the Paleogene and Neogene periods.