The Louisiana Purchase and the belief in Manifest Destiny affected the United States in the 1800's by -

As a result of the deal, the U.S. gained control of the powerful Mississippi River, doubled the size of the country and affirmed the idea for many that America's "Manifest Destiny"

Explanation:

answer; /// slavery should be outlawed in the new country, was part of the initial draft of the declaration of independence, but not part of the final