Fully aware of the legal situation regarding artifacts and the like. According to this: http://www.blm.gov/pgdata/etc/medial...ubliclands.pdf
It's 100 years, I've read similar information from other states that says 50 years I believe that may only be applicable to some locations. Minerals on the other hand are pretty much free game (I think 250# per year per person before you need a permit)
Generally we're scrounging in dumps from the 50's/60's/70's, figure we'd have to dig waay to much to find anything fun from earlier times anyway. All we've found of interest has been bits of unidentifiable but interesting metal, and a bottle with my wifes year of birth on the bottom which was kinda amusing. We mostly just scrounge around and look at stuff or take pictures anywho.
Good to point out the rules though.