A mapping of the flow conditions of the Mach 4 Quiet Ludwieg Tube has been completed. This report completes a prior investigation by Flood et al. . That paper provided preliminary results, which stated that the maximum quiet flow capabilities of the facility were a total pressure of pt1 = 95.4 kPa (13.8 psia) and a unit Reynolds number of Re′ = 4.27 × 106 m−1 . Recent improvements to the tunnel operation and data acquisition procedures have improved this to pt1 = 97.9 kPa (14.2 psia) and Re′ = 4.54 × 106 m−1 . The length of the quiet core and the Reynolds number based on quiet core length at pt1 = 96.5 kPa (14.0 psia) are measured to be ∆xqc = 97.7 mm and Reqc = 4.32 × 105, respectively.