The spectrum of the cosmic background radiation peaks at 6/cm and falls rapidly at higher frequencies. The experimental determination of this simple but important fact has had a long and troubled history. It remained in doubt long after the nature of the Rayleigh-Jeans region of the spectrum was firmly established. In this review, the experimental difficulties which have plagued cosmic background measurements at and beyond the peak in the spectrum are described. A critical evaluation of the present status of the field is then given.