Why did americans want to control the mississippi river?

Because it was the principal highway to move men and supplies the whole length of the country, from the blockade-runner's port of New Orleans right up into the heart of the Union

Control of the Mississippi River was important to both sides during the American Civil War. The North wanted to control the river and split the Confederacy in two. The South wanted to maintain control and ensure the flow of supplies back and forth across the river.

The Mississippi became an important route for transport and trade early in the 19th century. It is navigable from the Falls of St. Anthony in Minneapolis to its mouth. Cargo ships, barges and even paddle steamers transport both cargo (grain, paper, cotton, iron and steel) and people along the Mississippi. Cities and industries have grown up along the banks of the Mississippi because it is a natural waterway fro transporting goods.

White dwarf is very hot, but also very small and that is why it may appear dim.