  We provide a comprehensive study of the cosmic-ray muon flux and induced
activity as a function of overburden along with a convenient parameterization
of the salient fluxes and differential distributions for a suite of underground
laboratories ranging in depth from $\sim$1 to 8 km.w.e.. Particular attention
is given to the muon-induced fast neutron activity for the underground sites
and we develop a Depth-Sensitivity-Relation to characterize the effect of such
background in experiments searching for WIMP dark matter and neutrinoless
double beta decay.
