We review the properties of 40 X-ray binaries that contain either a confirmed black hole or a black hole candidate. After discussing briefly the significance of these Galactic black holes to both astronomy and physics, we present basic data for all 40 systems, review the physics of mass accretion onto black holes, and then show seven-year light curves of 20 systems. The second half of this work is a far-reaching review of the canonical emission states of black hole binaries, which is based on X-ray, radio and gamma-ray data. For several selected black holes, we show 33 pairs of X-ray energy and power density spectra and use these spectra as a basis for introducing modified definitions of the canonical X-ray emission states of an accreting black hole. We highlight the physical structures and some of the emission mechanisms associated with each emission state. In the final pages we examine both low- and high-frequency quasi-periodic oscillations. A recurring theme of the review is the importance of these black holes as potential sites for tests of general relativity. Accordingly, we stress phenomena that originate in strong gravity, such as relativistic Fe emission lines and thermal continuum emission, both of which arise in the inner accretion disk. Especially important in this regard are the high-frequency (40-450 Hz) quasi-periodic oscillations observed for seven black holes, three of which show evidence for commensurate (3:2) pairs of frequencies.