Monroe Doctrine and Roosevelt Corollary--the Monroe Doctrine first set the policy that the western hemisphere was closed to colonization. The Roosevelt Corollary took it a step further by providing military behind the policy.
Following the independence movement in the US and throughout Latin America, the US wanted to protect the area from future colonization. The Monroe Doctrine made the statement and then 80 years later the Roosevelt Corollary enforced the doctrine with our navy and army force.
The Pyrenees mountain range.
B, the invention of techniques for farming and animal herding
By 1860 almost half of the American people lived west of the Appalachian Mountains. In the 19th-century movement of settlers into the American West, was initiated with the Louisiana Purchase and Lewis and Clark´s expedition. I was also triggered by the California Gold Rush, the Oregon Trail and "manifest destiny." Manifest destiny was the believe that Americans were meant to expand across all of North America.
