1. Manifest Destiny (add westward expansion western territories), annexation, cession (add cede, secession,) acquisition, territories, immigrant, emigrant, famine, persecution, oppression (add political and religious), Transcontinental Railroad, ethnic

2. Manifest Destiny
The belief that the United States was destined by God to extend its boundaries to the Pacific Ocean.
Annexation
The act or an instance of annexing, or adding to something larger, especially the incorporation of new territory into the domain of a city, country, or state.
Cession
1.) act of ceding, as by treaty.
2.) something that is ceded, as territory.
Acquisition
The act of acquiring or gaining possession: the acquisition of real estate.

3. Territories
1.) Any tract of land; region or district.
2.) The land and waters belonging to or under the jurisdiction of a state, sovereign, etc.
3.) Any separate tract of land belonging to a state.
Immigrant
A person who migrates to another country, usually for permanent residence.
Emigrant
A person who emigrates, as from his or her native country or region: They welcomed the emigrants from Italy.
Famine
1.) Extreme and general scarcity of food, as in a country or a large geographical area.
2.) Any extreme and general scarcity.
3.) Extreme hunger; starvation.

4. Transcontinental Railroad
Persecution
A program or campaign to exterminate, drive away, or subjugate people based on their membership in a religious, ethnic, social, or racial group: the persecutions of Christians by the Romans.
Oppression
1.) The exercise of authority or power in a burdensome, cruel, or unjust manner.
2.) An act or instance of oppressing or subjecting to cruel or unjust impositions or restraints.
3.) The state of being oppressed.
Transcontinental Railroad
A train route across the United States, finished in It was the project of two railroad companies: the Union Pacific built from the east, and the Central Pacific built from the west. The two lines met in Utah. The Central Pacific laborers were predominantly Chinese, and the Union Pacific laborers predominantly Irish. Both groups often worked under harsh conditions
Ethnic
1.) Pertaining to or characteristic of a people, especially a group (ethnic group) sharing a common and distinctive culture, religion, language, or the like.
2.) Referring to the origin, classification, characteristics, etc., of such groups.
3.) Being a member of an ethnic group, especially of a group that is a minority within a larger society: ethnic Chinese in San Francisco.