The first US Federal Census was taken in 1790 and since then a new census has been taken every ten years. A census must be 72 years old before it is available to the public and so the 1940 Census is the most recent census available for public use.
US Federal Census records contain important information about ancestors - like the address of the household and the name of the head of the household. You can also find the age or year of birth for individuals and in some census years find where individuals and their parents were born.
In some census years marriage and immigration information is provided and in some years information about education and occupation as well as whether the individual owned or rented the residence. See Census Records for lists of the census information that can be found for each census year.
You can use the information provided in individual census years to determine the ancestry of individuals and generate a basic family history that can be supplemented with information from other sources.
For example you might find a family that consists of a father, mother and children in the 1870 census. Then in the 1900 census you might find that some of those children now have their own families and so along with the other information provided by the census years you have 3 generations of family history. If there was a parent of either the father or mother in the 1870 census then you would have 4 generations of family history.
There are a number of ways to find census data. You can go to websites that provide census records online and then be able to obtain census data 24 hours a day, 7 days a week from any location that has Internet access.
You can visit a local library or historical society and in most cases find census data for the county in which the library or historical society is located. These census records will usually be on microfilm and can be read using microfilm readers provided by the library or historical society. This is usually free for members but in some cases there might be a nominal charge.
Most libraries also have Online Resources and in many cases they provide online access to the entire US census to library members. So using your library card number you can search the entire US census from anywhere that has an Internet connection. Most libraries today also provide library use of computers with Internet access and so you can use a library computer to find census data online.
The National Archives in Washington, DC and its thirteen regional facilities in the United States provides microfilm copies of each census at each of its locations. The National Archives also sells microfilm copies of each census. There are also other organizations like State Libraries and State Archives as well as genealogy sites like Ancestry.com and Family Search that provide census records online.
When you undertake a census search you don't know where the results will take you. For example, using an online census you can look at the census records for a small town in Pennsylvania and then with a few clicks be looking at the census records for a large city in California. See Search-California-Death-Index-For-Catherine-Holbrook and Search-US-Federal-Census-George-Kishbaugh to see case studies that use census records from different years and states.
If you are looking for the country of birth of an immigrant to the United States try looking in the US Census. If you can't find the immigrant in the US Census look for his or her children in the US Census.
You can find the father's place of birth and the mother's place of birth in many census years - 1880, 1900, 1910 and 1930.