Final answer:
The philosophy of Manifest Destiny, which espoused a divine right to expand, in conjunction with economic interests, justified American territorial acquisition. Advances in technology and gains in trade opportunities provided further rationalization, even as expansion raised complex issues regarding culture and administration.
Step-by-step explanation:
Understanding Manifest Destiny and American Expansionism
Americans rationalized the continuation of territorial acquisition through the philosophy of Manifest Destiny. This belief positioned Americans as having a divine right and duty to govern and civilize other groups encountered during expansion.
Technological advancements like railroads and the telegraph were seen as tools of civilizing influence. Manifest Destiny also served as absolution for any dubious tactics used in the process of expansion.
The concept of Manifest Destiny promoted the notion that the United States was destined to spread democratic institutions and encompass the entire continent, from the Atlantic to the Pacific.
This belief rendered the presence of Hispanic communities, Western European settlers, and diverse tribes as mere obstacles in the path of a preordained expansion.
The underlying economic motivation for expansion was equally vital, as acquiring new territories through treaties, land purchases, and wars was seen as a means to access new resources and opportunities for trade, such as with Asia after securing important ports like San Diego and San Francisco.
The United States' decision not to annex all of Mexico after the Mexican-American War reflects the complexity of expansionist attitudes.
The thinly-populated territories were viewed as ripe for settlement by Caucasian Americans, whereas the more densely populated areas with a history of mixed ancestry presented cultural and administrative challenges that were deemed impractical to overcome.