At the high school level, I (Ms. Coady) had students research their family tree by using the last available census from 1940. I explained the reason why the census exists:
According to the census site, "Census results help determine how billions of dollars in federal funding flow into states and communities each year...The results determine how many seats in Congress each state gets...It's mandated by the U.S. Constitution in Article 1, Section 2: The U.S. has counted its population every 10 years since 1790."
Students then went to the TCPL database site and found the genealogy databases. Most of them have to be used on site but HeritageQuest Online does not. If you're looking for a fun project to do with your family, check it out! Students whose families didn't come to the US until much later got to research famous figures so if that is the case with your family, check out this page. Have fun exploring!