The Transiting Exoplanet Survey Satellite (TESS) will be conducting a nearly all-sky, photometric survey over the course of two years, with a core mission goal to discover small transiting exoplanets orbiting nearby, bright stars. The satellite will obtain 30-minute cadence observations of all objects in the 26 TESS fields of view and 2-minute cadence observations of 200,000 to 400,000 selected stars. The choice of which stars to observe at the 2-min cadence is driven by the need to detect small, transiting planets, leading to the selection of primarily bright, cool dwarfs. We describe the integration of numerous astronomical catalogs and the algorithms used to assemble the TESS Input Catalog. We have created a preliminary Candidate Target List using a ranking system for all stars in the sky, according to the smallest transiting planet detectable. We also discuss additional factors that affect the ability to photometrically detect and dynamically confirm small planets.