Abstract: A detailed and statistically robust visual inspection of the SDSS DR7 imaging footprint, and similarly the entire RCS-2 cluster catalog, has produced hundreds of candidate cluster-scale strong lensing systems, over a volume of approximately 9 Gpc^3 out to a redshifts beyond z=1. An extensive multi-wavelength multi-telescope follow-up program has confirmed the lensing interpretation of several hundred of these lensing candidates, providing a dramatic increase the total number of known lenses from all previous samples. The resulting samples probe strong lensing from group mass scales all the way to the most massive clusters, covering two orders of magnitude in mass. These lenses inform our understanding of massive dark matter halos through studies both of the statistics of the source images and lenses, and detailed lensing studies of individual systems. The highly magnified images of the lensed sources also provide a unique view into star formation in the early universe, probing spatial and mass scales otherwise not accessible with current telescopes.