Lewis and Clark were not the first explorers to visit the Sandy River Delta. A scouting party for Capt Vancouver had come there from the Pacific Ocean in 1792. However, Corps of Discovery members left a better description.

When the Corps stopped at the delta on November 3, 1805, they found a lot of sand and named it the Quicksand River, unaware that it was sediment from a recent eruption of Mt Hood. Four months later, on their return east, they camped in the area again for several days.

One Corps member, Whitehouse, wrote that one village there “was by far the handsomest of the kind that we had yet seen.” In another place, Capt Clark noted many small canoes on the bank, and saw women using them to collect wapato:
...with one of these [canoes] a woman enters a pond...and by means of her toes and feet breakes the bulb of this plant loos from the parent radicle and disincumbering it from the mud it immediately rises to the surface of the water when she seizes it and throws it into her canoe...they will remain in the water for hours together in surch of this bulb in middle of winter.