In 1970, there were less than a million Mexican-born people in the United States. In the next 40 years, that number surged to more than 12 million.
But in the last couple of years the Mexican-born population of the United States has started to decline.
According to a new a report (PDF) from the Pew Hispanic Center, net migration from Mexico is now zero.
In fact, the report suggests that more Mexican-born people may now be leaving the US than arriving. This means the end of the largest and most sustained immigration trend in American history.
The co-author of the report and senior demographer with the Pew Hispanic Center, Jeff Passel, says the reasons include the economic downturn in the United States; the comparative prosperity of Mexico; tougher border controls; increased deportation of undocumented immigrants.
Also, organized crime gangs inside Mexico are making life difficult and dangerous for illegal immigrants.
Underlying it all is the changing demographic picture of Mexico, which has seen birth rates plunge, especially in the last 20 years.
"Even if things change, (and) the US economy came back," says Passel, "there's not as many Mexicans to migrate to the US as there was 20 years ago."