Mexican-born immigrants are the majority, comprising 28 percent of the 41 million total immigrant populations.

Mexican immigration to the United States has gone through several waves starting before World War II, continuing with programs for seasonal farm labor.

Although the number of Mexican immigrants remains the highest in the country, in recent years it has started to decline as a result of recession, improved educational and economic opportunities at home, and tougher border enforcement.

Meanwhile, immigrant groups from India and China, including Hong Kong, but not Taiwan, each account for about 5 percent of the United States' total immigrant population; many moving to the country to work, study or join family members already here.

The Philippines has the fourth highest number of immigrants living in the United States at 4 percent, while residents from Vietnam, El Salvador, Cuba and Korea each make up 3 percent of the immigrant total.

Up until the mid-1960s, immigration restrictions in the United States favored the entry of people from Europe.  However, with the passage of the Immigration and Nationality Act - a law that made it so people would be admitted based on their occupational skills rather than their country of origin - the makeup of most immigrants also changed from Europe to Latin America and Asia.

In 1960, Europeans made up nearly 75 percent of the U.S. immigrant population, but by 2013 that number dwindled to just 11.6 percent.  During the same period, immigrants from South and Central America increased from 19-to-54 percent.

Source: Voice America