What two cities were important trade centers because of their location on major rivers?

Memphis is located on the Mississippi River, which is a major transportation route for goods and services. The city is also home to several major railroads, making it a hub for transportation in the region. St. Louis is also located on the Mississippi River, and is also a major transportation center. The city is home to several major highways and railroads, as well as the St. Louis Lambert International Airport, making it a major hub for transportation in the region.