Nationalchamps.net's all time database records us as having a NC in 1908. Is that one generally accepted? If so, why don't we have a flag for that one? Aren't there some different factors involved?
I think there's some cut-off point in the 1930's or 1940's where they consider "modern" college football starting off. I don't think the university generally acknowledges 1908 as a national championship.
USC is kind of in a drought being they haven't won a National Championship since 1978. That's too bad, there is now officially a "tear in my beer."