Europeans began to structure their economies around international trade during the Commercial Revolution.
The South relied heavily on steamboats for transportation of supplies and troops. They absolutely needed the Mississippi River to be effective in anyway during the war. The North also used it for transporting, but they had railroads. They were mostly concerned with keeping the South from using it.
The answer is
- <u><em>geothermal</em></u>
- <u><em>hydroelectric</em></u>
<em>Hope this helps!!!</em>