Back before the Caltrans era, the Division of Highways considered macadam pavement as "oiled earth" and marked it on the maps as such, even though driving over it was only marginally different than driving over asphalt, right down to the painted center lines on the carriageways. When I acquired my first official state highway map back about '63, I was shocked to see many state highways, particularly those in the San Joaquin Valley as well as in the Sierra Nevada -- extending all the way up into NE CA, showing that they were "oiled earth", although I had ridden on them and assumed they were simply asphalt (albeit more prone to ruts than other roads on which I had traveled). My cousin-in-law, who worked for the Division, set me straight on that; he also mentioned that they were in the process of re-doing all but the least travelled (e.g., what's now CA 172 or CA 36 west of Red Bluff) with modern asphalt overlays. It's likely the CA 41 surface back in the day was indeed some type of macadam; that surface type likely persisted until the route was realigned (which would have been just about the same time as the alphalt overlay program).