How was the wave of UIS. immigration in the late 1800s different from the previous wave of immigration in the mid-1800s?

"In the late 1800s, people in many parts of the world decided to leave their homes and immigrate to the United States. 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, and nearly 12 million immigrants arrived in the United States between 1870 and 1900. During the 1870s and 1880s, the vast majority of these people were from Germany, Ireland, and England - the principal sources of immigration before the Civil War. Even so, a relatively large group of Chinese immigrated to the United States between the start of the California gold rush in 1849 and 1882, when federal law stopped their immigration."

https://www.loc.gov/classroom-materials/united-states-history-primary-source-timeline/rise-of-industrial-america-1876-1900/immigration-to-united-states-1851-1900/

b europeans take corn to africa. corn becomes an important crop there.