In the standard cosmology of the Big Bang theory the cosmic microwave background (CMB) is the remnant radiation from the hot early universe. The sky signal is comprised of radiation from the CMB, from Galactic emission, from atmospheric emission, and from instrument sidelobes seeing the ground and man-made interference. One observes in directions of minimum galactic signal. The antarctic polar plateau provides the best site in the world for low atmospheric emission, low horizons, low man-made interference, and reasonable accessibility. The low column density of precipitable water and extreme stability for periods exceeding a week, combined with low RFI are critical. A very important secondary benefit for anisotropy experiments is the ability to observe the same part of the sky continuously at a high elevation angle.