  Recent numerical simulations of globular clusters (GCs) have shown that
stellar-mass black holes (BHs) play a fundamental role in driving cluster
evolution and shaping their present-day structure. Rapidly mass-segregating to
the center of GCs, BHs act as a dynamical energy source via repeated
super-elastic scattering, delaying onset of core collapse and limiting mass
segregation for visible stars. While recent discoveries of BH candidates in
Galactic and extragalactic GCs have further piqued interest in BH-mediated
cluster dynamics, numerical models show that even if significant BH populations
remain in today's GCs, they are typically in configurations that are not
directly detectable. We demonstrated in Weatherford et al. (2018) that an
anti-correlation between a suitable measure of mass segregation ($\Delta$) in
observable stellar populations and the number of retained BHs in GC models can
be applied to indirectly probe BH populations in real GCs. Here, we estimate
the number and total mass of BHs presently retained in 50 Milky Way GCs from
the ACS Globular Cluster Survey by measuring $\Delta$ between populations of
main sequence stars, using correlations found between $\Delta$ and BH retention
in the CMC Cluster Catalog models. We demonstrate that the range in $\Delta$'s
distribution from our models matches that for observed GCs to a remarkable
degree. Our results further provide the narrowest constraints to-date on the
retained BH populations in the GCs analyzed. Of these 50 GCs, we identify NGCs
2808, 5927, 5986, 6101, and 6205 to presently contain especially large BH
populations, each with total BH mass exceeding $10^3\,\rm{M_{\odot}}$.
