There were some negative effects that arose from the policy of Manifest Destiny. The policy of Manifest Destiny was the desire of the American people to spread their way of living over all of the lands between the Atlantic Ocean and the Pacific Ocean. As a result of the westward movement of the American people, Native Americans suffered greatly. In the 1830s, Native Americans were forced to move to lands west of the Mississippi River. Then, when Americans moved further west, they had to give up the lands that they had received that were located west of the Mississippi River. There were many battles with the United States Army, many of which the Native Americans lost. Their way of life was destroyed, and they suffered greatly from diseases that were spread as the American people moved onto the lands of the Native Americans.

The policy of Manifest Destiny also led to a war with Mexico. The United States had long wanted to take over what is now the southwest part of the United States. However, this land was controlled by Mexico. Mexico had no intention of selling it to the United States. When the United States moved their military into the land that was in dispute, Mexicans attacked American troops. This led to the start of the Mexican-American War. While the United States won this war, the actions of the United States were largely responsible for the start of the war.

As a result of the policy of Manifest Destiny, the United States gained a great deal of land. This led to many disputes regarding whether slavery would or would not be allowed in these territories. Because compromises failed to permanently resolve the issue about the spread of slavery, the United States would ultimately enter into civil war.

There were some negative consequences of the policy of Manifest Destiny.