  A peak has been unambiguously detected in the cosmic microwave background
(CMB) angular spectrum. Here we characterize its properties with fits to
phenomenological models. We find that the TOCO and BOOM/NA data determine the
peak location to be in the range 175--243 and 151--259 respectively (both
ranges 95% confidence) and determine the peak amplitude to be between ~70 and
90 micro Kelvin. By combining all the data, we constrain the full-width at
half-maximum to be between 180 and 250 at 95% confidence. Such a peak is
consistent with inflation-inspired flat, cold dark matter plus cosmological
constant models of structure formation with adiabatic, nearly scale-invariant
initial conditions. It is inconsistent with open and defect models.
