In 1828 a Hudson's Bay Company brigade leader named the river the Unknown River, then watched it vanish into a swamp. Over seventeen years it was called by six names, all given by outsiders, until John C. Frémont's 1848 map honored Alexander von Humboldt, who never saw it. The episode asks what the sequence shows about naming and power, and notes that no Indigenous name for the whole river was found.
No one agrees who Mary, the namesake of Mary's River, was. Whether Frémont traveled the river he named is disputed between a state chronology, which says he did not, and a Winnemucca marker, which says he did.