Lidars have been used extensively to derive temperatures, but not absolute densities, in the mesospheric region of the atmosphere. We used observations since 1993 with the Rayleigh- scatter lidar at the Atmospheric Lidar Observatory (ALO) at Utah State University (41.7oN, 111.8oW) to create an absolute density climatology between 45 and ~95 km. The observations provide profiles of relative density to which an absolute scale is attached by normalizing the profiles at 45 km to the densities in the MSISe00 empirical model. We examine the density variations on several time scales—during the climatological year, from year to year, and over several weeks. We also compare the densities to those in the MSISe00 model.