It used to be the only alternative was looking thru microfilm records at the library so the census indexes that were published in books or online could save time. Although they are helpful they are only as good as the person who did them.
Consider the death record of Denard Roberts Fulford. It shows he was born in the Dakota Territories. I've seen this fact copied into a number of online family trees.
But when I looked at this and the other members of his family, it just didn't make any sense. His father and mother were born in North Carolina as were all his siblings.
How did his folks travel all the way to the Dakotas for his birth and then back to North Carolina for the others? Every census record I found for him and his father was in North Carolina.
When I finally got an opportunity to see the original, instead of the Dakota Territories, what I found was DK or "don't know."