For many of us, knowing where our ancestors came from is a primary goal. Here are some tips on where you might start looking.
1850 ? 1940 U.S. Census records. Census records list the person's birthplace; 1880 ? 1930 also list parents' birthplace. This is obvious place to start looking! Make sure to check every relevant year ? information may vary for any given person. Also check siblings and cousins for consistencies and other clues.
Check the neighborhood. Is everyone in the neighborhood on a census from the same place. That might be a clue as to where your family came from even if your ancestor is listed as being from the U.S.
Death certificates. Some death certificates ask for parents' names and places of birth. Makes sure to look at death certificates for siblings and cousins for the information as well.
Family histories. Family histories often discuss the origins of the family. Not every detail may be correct, but they are worth a look.
DNA. Your DNA won't tell you which line came from where but it will give you some clues. And always test your oldest family members to narrow your search.
Ancestry also has lots of great research guides with more information on finding foreign ancestors