Very much so. With regard to the Mississippi, the site near St. Louis was home to one of the greatest known prehistorical cities in North America, Cahokia. One of the more famous finds published about four years ago was the widespread use of "black drink," a ritually important substance made between 1000 and 1250 from holly leaves and local water.

The leaves, roasted before being steeped in hot water (acquired locally), produced a highly caffeinated drink that was then drunk rapidly in excess to induce vomiting as part of a purification ritual. This ritual lasted well beyond the Cahokian period; it's part of the reason why that particular holly, the Yaupon, is known as Ilex vomitoria.

The drink is evidence not only of cultural practices but of large-scale trade. The Yaupon grew only near the Gulf of Mexico, hundreds of miles away from Cahokia.

In the historic era, there is ample evidence of the Mississippi being used at St. Louis as a source of drinking water. The 1858 Sketch Book of Saint Louis contains an entire chapter devoted to "The Water-Works," and it describes on pages 69 and 70:

"The Missouri river imparts its peculiar muddy caste to the Mississippi at and below their junction, and although the appearance of the water is not clear, and to a stranger is rather disagreeable, yet it is nevertheless about the best river water in the world. It is said to keep longer and be sweeter on a sea voyage than the water of perhaps any other stream; indeed it may almost be said never to spoil."

There remained shortages due to a lack of supply, and even the Sketch Book, which is pretty hagiographic, states:

"It does not, however, agree with all who use it; until they become habituated. Some of those especially Europeans who after a long confinement on ship-board, and a scant supply of water, find themselves in the midst of such a river and particularly if the weather is hot, with power to drink just as much as they please, are very apt to be rather seriously affected by its use."