The extraordinary revelations from the 2010 census that the nation’s Hispanic population has surged to historic levels has understandably alarmed some fearful that the country is changing too fast, too furiously. For the first time in modern world history, a major nation is changing color right before the eyes of its residents.

I argue the transformation will help renew and replenish the country, and let me add what I said on "Fox and Friends" Friday morning: America has been here before.

It happened in the middle of the 19th century at exactly the time we were going west, defeating Mexico, suppressing the tribes and fulfilling our manifest destiny. Hundreds of thousands of illegal, that is, undocumented -- unsanctioned, and uninvited -- immigrants, mostly Catholic, many from Germany, but many more from Ireland, poured into American cities up and down the East Coast.

In the case of the Irish, they were driven from home by poverty, aggravated by the disastrous potato famine of 1847-48 and exacerbated by chronic, severe oppression by the English rulers and ruling class.

This giant surge of men, women and children abandoned their stricken homeland. Entire cities, villages and towns were deserted in the Old Country and a questing, undaunted and desperate community of refugees came ashore en mass in New World cities like New York, Boston, Charleston, Savannah and, to a lesser extent, New Orleans.

In those two years alone, a staggering 650,000 Irish men women and children arrived in New York, in a historic instant becoming almost a third of the city’s population. By 1850, the Irish made up 43 percent of the city’s foreign-born.

One reaction to the tsunami of Irish was the rise of militant anti-Catholic gangster/activists like William “Bill the Butcher” Poole, a real figure from history whose story is fictionalized in the Martin Scorsese film "Gangs of New York," (which is based in turn on Herbert Asbury’s classic novel). Alarmed that the Irish newcomers would overwhelm the Anglo Protestant descendents of the nation’s founders and give control of the country’s political processes to the pope, Poole and his cohorts resorted to violence, intimidation and thuggery.

Anti-Irish gangs were formed; rioting and vandalism became commonplace, and, routinely, signs reading “Positively No Irish Need Apply” appeared on businesses and residential buildings. The militants formed their own political party, the Know-Nothings, which fought to suppress Irish immigration and keep newcomers from becoming naturalized citizens. The warring factions were constantly at each other’s throats, until the onset of the Civil War damned the nation to live through a far more catastrophic conflict.

And guess what happened when peace came. America had changed the immigrants far more than the immigrants changed America. The Irish assimilated, like the Italians, the Eastern European Jews and all the others who followed them to the shores of our New World Colossus.

And so it will happen with the Latinos.

Already, as the 2010 census makes clear, the biggest share of the Hispanic population explosion comes from children who are American-born. They are poorer and less educated than many others. But most of their parents are filled with the kind of immigrant vigor that eventually made the Irish such magnificent Americans.

Geraldo Rivera is anchor of "Geraldo at Large" on Fox News Channel. Watch "At Large" this weekend on Saturday and Sunday evening at 10 p.m. ET.