Rhus republicensis is known from specimens which are recovered from an outcrop of the early Eocene, Ypresian[1][2] Klondike Mountain Formation in Republic.

[2] The plant community preserved in the Klondike Mountain formation is a mixed conifer–broadleaf forest with large pollen elements of birch and golden larch, but also having notable traces of fir, spruce, cypress, and palm.

The type series specimens are currently preserved in the paleobotanical collections of the Stonerose Interpretive Center in Republic, Washington.

The etymology of the chosen specific name republicensis is a reference to Republic, Washington where the collecting site is located.

They noted that the Klondike Mountain Formation preserves a number of Rhus specimens which appear to be hybrids of the named species.