Neither Thompson nor Lewis and Clark were originators of the name. They gave us only the English translation of a name already long in use. "This river," say Lewis and Clark, in their journal for the day of their arrival at the mouth of the now noted stream, "had been known to the French as the _Roche Jaune_, or, as we have called it, the Yellow Stone." The French name was, in fact, already firmly established among the traders and trappers of the North-west Fur Company, when Lewis and Clark met them among the Mandans. Even by the members of the expedition it seems to have been more generally used than the new English form; and the spellings, "Rejone," "Rejhone," "Rochejone," "Rochejohn," and "Rochejhone," are among their various attempts to render orthographically the French pronunciation. Probably the name would have been adopted unchanged, as so many other French names in our geography have been, except for the recent cession of Louisiana to the United States. The policy which led the government promptly to explore, and take formal possession of, its extensive acquisition, led it also, as part of the process of rapid Americanization, to give English names to all of the more prominent geographical features. In the case of the name here under consideration, this was no easy matter. The French form had already obtained wide currency, and it was reluctantly set aside for its less familiar translation. As late as 1817, it still appeared in newly English-printed books,[B] while among the traders and trappers of the mountains, it survived to a much later period. [B] Bradbury's "Travels in the Interior of America." See Appendix E. By whom the name _Roche Jaune_, or its equivalent form _Pierre Jaune_, was first used, it would be extremely interesting to know; but it is impossible to determine at this late day. Like their successor, "Yellow Stone," these names were not originals, but only translations. The Indian tribes along the Yellowstone and upper Missouri rivers had names for the tributary stream signifying "yellow rock,"[C] and the French had doubtless adopted them long before any of their number saw the stream itself. [C] The name "Elk River" was also used among the Crow Indians.