The major ice sheets had retreated northward from much of Montana, but glacial lakes still occupied some basins and meltwater rivers were actively shaping the landscape.

The climate was warming but variable — not the stable, mild conditions of the Holocene that followed but a world of rapid climate shifts and unstable ecosystem boundaries.

The plant communities of the region were in transition.

Species that had been present during the glacial maximum — including cold-tolerant grasses and forbs adapted to the cold, dry conditions of glacial climate — were being replaced in some areas by species adapted to warmer conditions.

The transition was creating a patchwork landscape with high plant diversity in some areas, as different species tracked the shifting climate conditions.