Great question, and there's a lot of good parallels. In the early 19th century, the United States was much more vocally anti-immigrant than it is today, possibly because the country's demographics were so uniform. The real immigrant boom didn't come until the 1840s, and it came from two events (or categories of events): The Irish famine and the failed revolutions of 1848.

The immigration statistics have some problems in the 19th century, but the U.S. Census department does have some commonly used figures that you can look at. If you look at those figures, you see the surge (delayed by a few years, as trends tend to be).

Take Irish immigration: In 1846, 41,752 Irish immigrants came to the United States ─ almost a third of all immigrants from all countries counted in that year. Five years later, at the peak of Irish immigration, there were 221,253 Irish immigrants, representing a little over half of all immigrants entering the United States that year. Keep in mind that this was in a year when there were only about 23 million people in the United States all told. That immigrant surge, in just one year, represented nearly 1 percent of the whole U.S. population!

And Germany/Austria-Hungary was little different. The statistics here are less clear (the U.S. government didn't break out Austria-Hungary immigration until later) but still remarkable. In 1851, there were 72,482 immigrants from "Germany". Three years later, there were 215,009. Again, that's a little less than 1 percent of the entire U.S. population ─ in just a single year.

In a five-year span, from 1851 through 1855, more than 1 million German and Irish immigrants came into the United States. This surge represented a bit more than 4 percent of the total U.S. population. If such a surge happened today, it would be equivalent to about 12.8 million people, or New York City and Los Angeles (city limits only) combined.

Naturally, this kind of radical demographic change drew a strong response. In 1843, a Pennsylvanian Jew named Lewis Charles Levin became the leader of the American Republican Party, a nativist and anti-immigrant party that pledged to purify the United States and remove Catholic influence from the United States.

After a series of riots in 1844, Levin was elected to Congress. His mission, he told voters, was to require new immigrants to live in the country for 21 years before becoming citizens; to allow only Native-born Americans to be elected to office; and to remove foreign interference (this being interpreted as Catholicism, widely believed to be led by the Pope) from the United States.

Levin's American Republican Party spread, operating under different names in different areas. You might see it referred to as the Native American Party in places. This movement was most popular in the eastern coastal cities that welcomed the vast majority of immigrants.

The movements of the American Republican Party and Native American Party are a free-wheeling story of mid-19th century politics, full of bribery and scandal (just as all parties were back then). By the early 1850s, the movement had gone national, and in 1855, it largely coalesced under the name the American Party.

But that party was still only one part of the movement. Just as the tea party movement doesn't include a true political party, so too was this nativist movement, which became known as the Know Nothing movement.

While there wasn't enough national support to back immigration restrictions on the scale the most radical of the Know-Nothings wanted, the U.S. Congress did pass some pretty key legislation. The Act of 1855, for example, required the U.S. government to report the number of immigrants into the country each quarter ─ the better to keep track of the issue.