Why did many immigrants come to the united states during the second half of the 19th century

Fleeing crop failure, land and job shortages, rising taxes, and famine, many came to the U. S. because it was perceived as the land of economic opportunity. Others came seeking personal freedom or relief from political and religious persecution. ... Immigrants entered the United States through several ports.

Explanation:

the answer is a. hope this

i believe it would influence their own way of understanding things. it shall be a foundation where they can draw or start an argument.   historians are also  scientists that  have their tools of analysis and expertise to unlock a variety of difficulties such as relationships of man, origin, politics, economy, and culture. based on facts and understanding on these areas, they may shade light to extract ideas and develop options to validate a hypothesis or debunk it.