Have you obtained copies of your parents' records (B/M/D)? Have you found the same types of records for your grandparents? Also, have you checked census, military, obituaries, land, and probate records for each of those family members and obtained copies of the records? If not, I'd urge you to do so. These records can provide clues as to locations in which you can search for more records about your family, sometimes even giving very specific information regarding places and time periods to use for further searches.