High Resolution Measurements of the Microwave Background with the Cosmic Background Imager

The Cosmic Background Imager (CBI) is a 13-element interferometer designed to image intrinsic anisotropies in the cosmic microwave background (CMB) on arcminute scales. The CBI is located high in the Chilean Andes near the future ALMA site, and has been in full operation at this site since early January 2000. Observations over this period have revealed for the first time the existence of a strong drop in the CMB anisotropy spectrum between degree scales and scales of about 10 arcminutes (L ~ 1200), confirming one of the major predictions of standard theories of structure formation. These observations are discussed, as well as more recent developments at higher L. We also discuss the CBI's program to determine the Hubble constant from Sunyaev-Zel'dovich Effect measurements in low-z galaxy clusters, and survey other topics that the CBI is expected to address in the near future.