For rural areas, check the Assesor's Maps.
But if your doing an RS, don't you have deeds and other records that your working from? Don't those records (at least some of them) have this info?
If you are working within the bounds of an old Rancho or Townsite, you either aren't (in the case of a Rancho or many older Townsites) in a section, or may not be in one (depending upon age of Townsite).
These would be considered "omitted lands" from the PLSS survey. If your survey falls within omitted lands, then refer to the Rancho or Townsite, or whatever the case may be.