Publicly available witness reports, catalogued by military and civilian agencies, of Unidentified Aerial Phenomena (UAP) from 1947 to 2016 were hand-sorted for selection based on four criteria: reliability of witness testimonies, object angular size greater than 0.15 degrees, sufficient lighting, and sufficient information detail. The resultant database comprises the subset of historical UAP reports that were determined to likely represent unidentified aerial objects. Out of more than 100,000 reports amassed from one military database and four civilian databases, 301 reports spanning the same years were identified as meeting these criteria. From this selected set, the characteristics of shape, size, kinematics, electromagnetic effects, and sound emanation are examined. Detailed descriptions in the witness accounts allowed us to present scaled illustrations for the two most common UAP shape categories: disks (domed, elongated, shortened) and triangles (isosceles, equilateral). The largest shapes reported were diamond/rectangle and boomerang (median 300 ft (91 m)), and the smallest were spheres (median 20 ft (6 m)). Triangles (median 170 ft (52 m)) were consistently reported to hover, did not produce electromagnetic effects, and were often noted to have an absence of sound. The combination of unusual kinematic range and absence of sound was found in 16 reports which specifically mentioned objects that hovered, travelled faster than Mach 1, and exhibited an absence of sound: disk (5), triangle (8), oval (1), sphere (1), and boomerang (1). The dataset of UAP characteristics presented here, based on 301 reliable witness reports, can be used to inform the design of the various UAP field instrumentation, detection algorithms, and propulsion hypotheses that are critical to the advancement of our understanding of UAP.