When thousands of europeans left there homes in the 1800's and 1900's how did this effect migration to the untied states.

Migration to the U.S. was enormous during the 1800s and early 1900s. The population of cities at ports of entry (Los Angeles and New York City) grew rapidly as immigrants poured into America. There was stiff competition for jobs. The new workers helped to build the nation’s infrastructure (roads, railroads, canals, etc). Africans were forced to migrate to work as slaves.

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explanation:

the monroe doctrine is the best known u.s. policy toward the western hemisphere. buried in a routine annual message delivered to congress by president james monroe in december 1823, the doctrine warns european nations that the united states would not tolerate further colonization or puppet monarchs.