You asked a really big question. I see that elsewhere on the forum Joan is telling you about the FHL. These libraries are a great resource for doing any kind of genealogical work, including census. I'll tell you the basics: US Census taking began in 1790 and is taken every 10 years. You can only access the census after 72 years, so the most recent Census you can see is the 1930. The 1890 census was destroyed in a fire years ago and most of it did not survive. Many censuses are indexed so you can find people without already knowing their exact address. Most of the 1930 census was not indexed, but the entire 1920 Census was indexed so it's a good place to start. There are 2 main ways to view the census. You can order microfilms and view them at the FHL and make copies, or you can view them on the internet at Ancestry.com. For ancestry you need a subscription, or many local libraries subscribe so you might be able to do it at the library. Ancestry has the 1920 Census indexed and they are working on the 1930. This forum's home page, genealogy.com, has the 1900 Census indexed and available by subscription. My favorite way is the FHL, but you have to pay 3.55 for each film you order and wait 2 weeks for it to be mailed to them. To find someone in the index you need to know the state they lived in at the time of the census and the full name of the head of the household, since that is how they are indexed. People are indexed by last name and coded with something called a soundex, so all names that sound the same are grouped together with the first names alphabetical. http://www.avotaynu.com/soundex.htmlhttp://www.avotaynu.com/soundex.html explains this system. Ancestry allows you to search by typing in the surname and first name and state and viewing each match. Finding out where people lived is a different story. Ask relatives which state they lived, where they were born, where their parents lived and were born. You don't need addresses, but at least get cities and states so you can search the census. When you find someone in the census you will be amazed - information varies by each census, but most since the 1880 census have names of all family members living together, ages, race, sex, marriage info, immigration and naturalization info, place of birth of them and sometimes their parents, literacy, education, and occupation. If you can get back to the 1850 census, it is the first one where all family members are listed. Earlier census are difficult to work with - only head of household and few details. Enjoy your quest.