In the 1800s, the notion of manifest destiny encouraged americans to think of the united states as the land between a. the atlantic ocean and the pacific ocean. b. the atlantic ocean and oregon country. c. the atlantic ocean and the appalachian mountains. d. the atlantic ocean and the mississippi river.

The answer is A: the Atlantic Ocean and the Pacific Ocean. The term Manifest Destiny was first used by John O'Sullivan, a newspaper editor in 1845, to describe the prevailing American mindset that all lands from coast to coast are destined to belong to the United States. This mindset was reinforced by the Lewis and Clark Expedition in the early 1800s, which scouted out the American West and came into fruition with the completion of the transcontinental railroad in 1869.