If you research Livingston County, Kentucky, especially around 1850, and use FamilySearch.org to access free census records, be aware that at least part of the 1850 Livingston County census is indexed as Lincoln County, Kentucky. For example, if you wanted to find Charles G. Halstead in 1850 and use his name, Kentucky and 1850 as the search parameters, it will show him living in Lincoln County, Kentucky, but if you look at the census image, you will see him living in Livingston County.
This is an indexing error and has been reported. I spoke with a nice man who promised to check into the problem. That was several days ago and it has not been done yet, perhaps due to the holiday weekend. I will check again in about a week to see if it has been corrected and, if not, another report will be sent.
In the meantime, be aware of the problem.