Track Reconstruction and Experience with Cosmic Ray Data in CMS

The CMS tracking system, comprised of silicon pixel and micro-strip detectors, is designed to provide a precise and efficient measurement of the trajectories of charged particles emerging from the LHC collisions. With over 70~million electronic channels and an active area of about $200\,\mathrm{m}^2$ it is the largest silicon tracker ever built. After a short introduction to the CMS tracker and to the track reconstruction algorithms, results from tracking with cosmic ray data are presented. First experience with cosmic ray tracking was gained in a vertical slice test involving various CMS sub-detectors. Additional understanding was obtained during the final assembly and surface commissioning of the silicon micro-strip tracker. Both data sets have been extensively studied, and a concise summary focussing on track reconstruction is given.