Required Reading: Classic resources you shouldn't research without.

When you began tracing your family tree, you probably didn't realize you'd need to acquire some legal expertise — that is, in laws that affected your ancestors' lives. Luckily, learning how legal history intertwines with your family's history isn't as tough as passing the bar exam. Governing the Hearth: Law and the Family in Nineteenth-Century America by Michael Grossberg (University of North Carolina Press) explains — in plain English — legal policies on common-law marriage, adoption, women's and illegitimate children's rights, child custody and other family affairs. Many laws Grossberg discusses remained on the books well into the 20th century.