How did the idea if manifest destiny change the american landscape by the 1860's?

Explanation:

Manifest Destiny was the idea that Americans were destined by God to rule North America. The term was first used by John O'Sullivan. He was editor and wrote for Democratic Review. In 1845, when Texas was annexed by the United States, He wrote in its favor to overspread the continent.

According to Manifest Destiny, the US westward Expansion was justified. The idea of manifest destiny changed the size of the United States. The Louisiana Purchase doubled the size of the country. Indian removal Act was another major step in subjugating the Indians and completing the westward expansion. We can say that the idea of " Manifest Destiny " came to be true as the US expanded in the West and with that new towns and cities were established. Although it led to settlements of whites, It also displaced the Natives from their land.

the border between arizona and new mexico is a thin, black line; this indicates a state boundary.

its correct: it's a thin line, and it's a state boundary, correct