How did people float their goods down the Mississippi?

Barges and Towboats

Explanation:

Each barge has a carrying capacity equal to 60 semi trailers.

A standard barge is 200 feet long, 35 feet wide, and when

loaded to its 1500-ton capacity needs a nine-foot depth of

water to float. Barges are cabled together into a "tow,"

which can be longer than three football fields. A standard

tow of 15 barges can be pushed by a single towboat. A

towboat may be 150 feet long, four stories high, and

6000 horsepower.