On the WA Parks Map I have (BC-2501-08), there is no Youmans Rd.. I think you mean E. Hoquiam Rd.. Google maps lists it with both names. I rode it last year but darned if I can remember how it is signed. From the Google map view, it looks like it is signed as E. Hoquiam Rd..
We received a notice from a cyclist on the road that the road name is Youmans Rd. so we changed it on the newest map, BC-2501-10. The change is noted on the addenda for BC-2501-08. Maybe it's signed differently at either end? We'll have to keep an ear out for future updates.