I live about 10 minutes from the Lake Guntersville Dam on the Tennessee River and I usually visit it several times each week. The Tennessee River is a navigable waterway with a significant amount of barge traffic. Among the commodities transported are grain, coal, and sand. I'm sure there are many other products transported on the river, but these are the products that I know of. 

Before 9/11 you could drive right up to the lock and watch the barges pass through.That experience was always interesting especially because you could talk to the guys working on the barge and the tug as they worked. I miss those experiences since right after 9/11 the government put up fences around the lock.