At least two population milestones have been reached in 2011. The most spectacular is that 7 billion people now live in the world . The second, and more meaningful to Americans, is that nearly 40 million immigrants  live in the United States today. The increase in our nation's immigrant population has generated considerable controversy, but that is not new. Amidst all the fears of newcomers failing to integrate into American society, we need to take a look back at how those controversies played out during earlier waves of immigration. We can learn a lot from that history.
Today, immigrants comprise 12.9 percent  of the U.S. population. In 1870, 14.4 percent of Americans were immigrants. From about 1860 to 1920, immigrants were a larger share of the population than they are today. Those were the years when our ancestors built enough to fill an entire continent and produce wealth for millions. The 2010 Census reports that nearly half of all immigrants are Hispanic or Latino, which is the largest ethnic immigrant group. Because of that most anti-immigrant sentiments are directed against them.
Immigration politics in the 19th century were much more vicious  than today and focused on specific ethnic groups. In 1890 Wisconsin Governor William D. Hoard  claimed that German-Americans were engaged in a conspiracy  to darken the understanding of the children, and called for native born Americans to fight alienism and selfish ecclesiasticism by closing all German language schools in the state and making education in government schooling compulsory. Catholic and Lutheran German voters threw him out of office. An 1889 Illinois state law required all educators at parochial and public schools in Illinois to teach in English. Outraged German-American voters forced the law's repeal in 1893. Slowly but surely Germans assimilated, learned English, and became Americans.
American holidays, like Columbus Day , mark the battlegrounds over these conflicts. The controversy over whether Columbus was a courageous explorer  or a brutal slave trader and murderer  (he was both) is a recent one. In the 19th and early 20th centuries he was a symbol of Catholic heritage and Catholic contributions to America. There was fierce anti-Catholic and anti-immigrant hysteria at the time (most immigrants then were Catholics, as they are today).
Christopher Columbus served as a powerful symbol for the Catholic immigrants who were struggling to become American. After all, one of their co-religionists discovered the continent that the America was built upon. Several private organizations like the Knights of Columbus , a private Catholic organization, helped immigrants by providing charity, creating social insurance for immigrants, and opposing discrimination. Columbus was popular among all Catholics, but especially amongst Italian-Americans. They began celebrating his discovery of the New World on October 12, 1866  in New York City.
It was only after the end of the last wave of Italian immigration in 1934 that a national holiday  celebrating the Italian explorer was created.
America's vast immigrant heritage is also evident in less formal holidays. The original Protestant settlers of the 13 colonies would have been horrified to know St. Patrick's Day  grew out of Irish Catholic meetings in Boston and eventually was extended to an encampment celebration in the Continental Army. Today, revelers of all religious and ethnic backgrounds become Irish for a day every March 17th.
This process is repeating itself with immigrants from Mexico. Cinco de Mayo  is a minor Mexican holiday to commemorate the defeat of the French by Mexican forces at the Battle of Puebla in 1862 . It is not Mexico's independence day , as several people think, and it is not widely celebrated in Mexico. But it is very widely celebrated in the U.S. by Americans of Mexican descent and the rest of us who look for any good excuse to barbeque or have a few beers. Cinco de Mayo is turning American before our very eyes.
Over time immigrants and their children become Americans and Americans pick up certain traits, traditions, and habits of immigrants. From the German tradition of the Christmas tree  to the Italian dish called spaghetti and the name of our currency , which was first minted as a thaler in Bohemia and transported by the Dutch to their colony of New Amsterdam which later became New York, immigrants continually add to our civilization.
Assimilation is quickened by the remarkable pace of immigrant entrepreneurship, which is more than double that of native born Americans according to the Kauffmann Foundation . Many immigrants start businesses to service their own communities, but they quickly grow to service as many Americans as possible because of profit opportunities. That's how Italian food, Greek food, and that odd Eastern European invention called the pickle  have spread into most American homes. The process is continuing with Mexican, Chinese, and Indian food.
This process of assimilation and cross-cultural pollination is repeating itself today between Mexican, Chinese, Central American immigrants, and native born Americans. We should be thrilled to live in a society that is so attractive, wealthy, and prosperous that 40 million immigrants want to call it home and are becoming Americans right before our eyes.