Registered with OpenStreetmap today and began edits. The first was a state road turned over to counties, and the remainder are county roads that are now named. I went over the US highway tag definitions, and settled on tertiary as the best match.

The problem is there's no exact match with the road system in the State of Georgia. Paved county roads tend to have the same width as state roads, and are heavily traveled, even in rural areas. Unpaved county roads can be heavily traveled as well, although they tend to be narrower. However, tract isn't a good match. Tracts tend to be what we call a "field road," or run through woods. Unassigned is probably a better definition than residential, which apparently is the default for Georgia county roads on OpenStreetMap.

My goal at this time is to work on the paved county roads first before moving to the unpaved. It's probably more accurate to describe them as tertiary.