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Based on the accounts of early fur trapper forays in the 1820s, beavers (Castor canadensis) were abundant along the Humboldt River at early Euro-American contact and an important resource for Great Basin Indian tribes, but by the late 19th century, they had been highly over-exploited. Excessive reduction of beaver from this region probably caused changes in stream channel morphology, reduced perennial wetlands, and altered riparian vegetation. However, as the result of hunting restrictions and re-introductions (1920s through 1950s), beaver populations have rebounded to inhabit much of their former range and possibly even areas where they did not occur before European contact. Over the last 20 years, beaver activity in northeastern Nevada has increased substantially as these animals respond to and contribute to the functionality of streams. Many wildlife species are favored by beaver-created habitat. The Columbia spotted frog (Rana luteiventris) and Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) are two sensitive species that are largely benefitted by beaver activity. Functioning as ecological engineers, beavers create pools of slow-moving water that serve as sites for frog reproduction and wet meadows for foraging habitat and protective cover. In northern Nevada, spotted frogs are closely associated with slow-moving or ponded surface waters that are clear and have little or no vegetation canopy cover. Habitat changes caused by beaver may increase the resilience of Great Basin spotted frog populations in the face of threats from drought, climate change, overgrazing by livestock, and predation. Beaver ponds also provide critical refuge for Lahontan cutthroat trout, allowing them to persist, especially overwinter, in many small headwater streams. Cutthroat survival may be higher in beaver ponds than free-flowing stream sections as temperatures approach lethal limits. Proper beaver management is essential for sustaining Columbia spotted frogs, Lahontan cutthroat trout, and a host of other wildlife species in the Great Basin.