Depends on where you live. In MI bringing wood from home is strongly discouraged due to the ongoing effort to stem the spread of invasive insects. As a result of this, decent quality, reasonably priced firewood is widely available from many private sellers around state parks and other camping areas. Once you get into the northern areas of the state, you can just stop at a sawmill and get all the cheap, nicely dried firewood you could ever want.
So check your local regulations before you load a half cord into the truck and head out.