what is the setting of the road?

McCarthy never gives us any specific place names. It is perhaps the not so distant future but even that is not told to us. He does give us a key hint earlier on in the novel:

They trucked along the blacktop. Tall clapboard houses. Machinerolled metal roofs. A log barn in a field with an advertisement in faded ten-foot letters across the roof which says, "See Rock City".

Rock City, if this is the one, is a natural rock formation on top of Lookout Mountain, outside Chattanooga, Tennessee.Other that that the setting is bleak as can be on a landscape that looks as desolate as Mars.