For most of its first 100 years, the United States’ doors to immigrants were wide open.

The United States needed settlers and, increasingly, laborers, so there were few restrictions on who or how many immigrants could come into the country.

The only requirement for entry was that one be able to pay for his or her passage to America.

But, starting in 1870, two significant changes began that culminated in the passage of legislation that effectively “closed the door” to immigration after 1924.

The first change was a dramatic increase in the number of immigrants coming to the U.S.

According to the 1870 federal census, there were nearly 5.6 million immigrants in the United States. By 1910, that number had more than doubled to 13.5 million immigrants.

The second change was a shift in immigrants’ countries of origin.

Before 1870, the majority of immigrants came from Northern and Western European countries, including Great Britain, Germany, and Ireland.

Starting around 1870, more and more immigrants came from Southern and Eastern European nations, including Russia, Italy, and Poland. Increasing numbers of immigrants from China arrived as well.

This new wave of immigrants was relatively poor, uneducated, and unskilled.

They practiced different religions, including Catholicism and Judaism, and most spoke little English.

Some people wondered whether these immigrants, who seemed so culturally different, could assimilate into American society.

The result was a national debate over whether America should impose immigration restrictions.

And if so, what would those restrictions look like? And to whom would they apply?

Should the government consider an immigrant’s wealth? education? skills? need? work ethic? country of origin?

The results of this debate effectively “closed the door” to open immigration, and these questions about the United States’ immigration policy continue in the present day.