The Cosmology Large-Angular Scale Surveyor (CLASS) is an instrument designed to test the "inflation" theory of the first trillionth of a trillionth of a second of the universe. In the most compelling verions of Inflation, gravitational waves are generated in the first moments of the universe. These gravitational waves, in turn, leave their imprint in the spatial polarization pattern of the cosmic microwave background. CLASS is designed to search for this pattern Polarization will be measured over very large regions of the sky with radiometers at 40 GHz, 90 GHz, and 150/220 GHz. Polarization filters at the input of these radiometers are rapidly switched to modulate the polarization coming from the sky, to distinguish it from polarization arising from within the instrument. The Republic of Chile has granted us permission to situate the instrument at 5200 meters (17,000 feet) altitude on Cerro Toco in the Atacama Desert of northern Chile, near the Llano de Chajnantor Observatory. The development of the CLASS instrument is funded,in part, by the National Science Foundation.