What area of the world are most of the areas acquired after 1850 in

Areas in the Pacific Ocean.

Although expansion has always been a feature of large territories, imperialism gained traction in Europe in the 1700s and 1800s. Initially, Americans were not involved in colonization. In fact, due to their experience as former colonists, Americans were often against imperialism. However, during the late 1800s, attitudes began to change. The United States colonized areas such as the Phillipines, Samoa and Hawaii. Most of the areas they acquired after 1850 were in the Pacific Ocean.

maybe #3? try that i think its correct

what do you mean