Answer:
Manifest Destiny, a phrase coined in 1845, is the idea that the United States is destined—by God, its advocates believed—to expand its dominion and spread democracy and capitalism across the entire North American continent. The philosophy drove 19th-century U.S. territorial expansion and was used to justify the forced removal of Native Americans and other groups from their homes. The rapid expansion of the United States intensified the issue of slavery as new states were added to the Union, leading to the outbreak of the Civil War.
Step-by-step explanation:
Louisiana Purchase
Thanks to a high birth rate and brisk immigration, the U.S. population exploded in the first half of the 19th century, from around 5 million people in 1800 to more than 23 million by 1850.
Such rapid growth—as well as two economic depressions in 1819 and 1839—would drive millions of Americans westward in search of new land and new opportunities.
President Thomas Jefferson kicked off the country’s westward expansion in 1803 with the Louisiana Purchase, which at some 828,000 square miles nearly doubled the size of the United States and stretched from the Mississippi River to the Rocky Mountains. In addition to sponsoring the western expedition of Lewis and Clark of 1805-07, Jefferson also set his sights on Spanish Florida, a process that was finally concluded in 1819 under President James Monroe.
But critics of that treaty faulted Monroe and his secretary of state, John Quincy Adams, for yielding to Spain what they considered legitimate claims on Texas, where many Americans continued to settle.
In 1823, Monroe invoked Manifest Destiny when he spoke before Congress to warn European nations not to interfere with America’s Westward expansion, threatening that any attempt by Europeans to colonize the “American continents” would be seen as an act of war. This policy of an American sphere of influence and of non-intervention in European affairs became known as the “Monroe Doctrine.” After 1870, it would be used as a rationale for U.S. intervention in Latin America.
effects:
Manifest Destiny greatly impacted the country, it was the push behind America's expeditious expansion into the West. Some examples of it's impact on the country are that it helped fuel western settlement, and pushed many Native American out of America.