This study encompasses the characterization of the newly-developed Transonic Wind Tunnel Facility at the University of Illinois at Urbana-Champaign. The flow quality was assessed by considering the flow angularity and turbulence intensity across the operating Mach number range of 0.3 − 0.7. It was found that the tunnel displays negligible flow angularities at all conditions tested. The turbulence intensity varied from 0.37% to 0.76% with the maximum intensity occurring for the M = 0.6 condition. The influence of the test section porous wall boundary on the aerodynamic performance of an RAE 2822 airfoil model was analyzed by using numerous porous walls having 6%, 12%, and 40% open-area ratios and different hole configurations, and by varying the plenum chamber height. In addition, the influence of the model aspect ratio was determined using two test articles with aspect ratios of 1 and 2. The 12% OAR, AR = 2 resulted in the best agreement with simulations; however, the need for data corrections is still necessary as the flow-field streamlines are still influenced by the local test section boundaries.