The Manson impact structure is a 36.5-km-wide, well-preserved crater centered 130 km northwest of Des Moines, Iowa, that formed about 74 Ma. Its diverse lithologies (sandstone, shale, carbonate; leucogranite, gabbro/diabase, gneiss, amphibolite) contain a wide range of shock damage. Seventy-six samples from drill hole 2-A (1953, drilled to a total depth of 144 m) and M-1 (1991, to 212 m depth), located on the upper eastern flank of the 12 km (at base) central peak, were analyzed by optical petrography to determine shock index values useful for determining several key aspects of shock level distribution and modes of emplacement. Core samples from the upper half of hole 2-A consist of breccia with clasts comprised mainly of biotite granites, granodiorites, and gneisses; these lithologies also dominate the crystalline basement blocks that make up the lower half of the 2-A core. Planar deformation features (PDFs) in quartz (2-6 sets/crystal) and feldspars occur at all depths; biotite is readily kinked and variably decomposed. A diagnostic shock feature in quartz (uncommon in feldspars), referred to descriptively as "toasting," may be an optical rather than a compositional phenomenon. Subdivision of larger quartz crystals into numerous polygonal interlocked domains (commonly with thin boundaries of clear, post-impact quartz) produces a distinctive polycrystalline texture; individual domains contain PDF sets, many having no continuity of orientations with neighbors. Feldspars may show internal melt flow and recrystallization; alternate albite twins are selectively more shock disordered and subsequently altered.Shock levels are higher in the upper 38 m of the 2-A core, decreasing downward over the next 81 m as the drill hole passed through the lower impact melt breccia into the crystalline rock megablock zone. M-1 units (distinguished overall by fewer PDFs in quartz) are mostly shales (with a few possibly melted clasts) and quartz sandstone (uncommonly with PDFs) in the upper 57 m; below this a 34 m interval of breccia with mainly leucogranite clasts having high shock indexes, characterized by extensive clast recrystallization and matrix glass; then 18 m of light and dark igneous and metamorphic clasts (variably shocked) with a few clasts of shocked sandstones and shales and some devitrified glass; and bottomed by 49 m of amphibole-rich suevite breccias with less obvious shock damage.