The 1870 census is sometimes referred to as the genealogy "brick wall" because for many African Americans it is hard to trace their family members beyond this document. However, with the use of the the many resources discussed in this guide and lots of hard work it is possible to discover family members pre-1870. If you hit the "brick wall" and can't find your family members in any censuses prior to 1870 the first question to ask is were they enslaved? There are clues in the 1870 census that can help to answer this question.
If you believe that your ancestors might have been enslaved, there are other ways to find information, which might include reviewing the many different types of documents held during slavery (i.e. planation records and cohabitation records). You can learn more about this in other sections of this guide.
These documents often have to be cross-referenced other documents, such as census records or probate records. Many of the handbooks mentioned in in this guide can be helpful with this task.