People came from a variety of nations and backgrounds. Between 1840-1860, over 1.5 million Irish people immigrated, hoping to escape the famine (extreme food shortage) at home. During the same period, over one million Germans immigrated in order to buy their own farms or start their own businesses.
Immigrants faced a lot of prejudice. Some U.S. citizens who opposed immigration were known as nativists because they believed immigration threatened the future of native-born Americans thought (and nativists today think) immigrants take jobs away from American citizens.
Congress responded to the nativist influence. During the late 1800s, Congress passed laws placing restrictions on immigrants. Not all of these laws were unfair. Some of them became the basis for requirements that immigrants must meet in order to become U.S. citizens.