The rim edge of Millikan is roughly circular and well-defined, but with some irregularities. There are some small outward bulges along the south and east where the edge has slumped inwards somewhat. The inner walls lacks a terrace structure that is seen, for example, in the smaller Cantor to the south. The interior floor of Millikan is relatively level, and there is a small, bowl-shaped crater to the north of the midpoint. Offset to the west of the middle is a low central peak. The floor is also marked by a number of tiny craterlets.
Menzel, D. H.; Minnaert, M.; Levin, B.; Dollfus, A.; Bell, B. (1971). "Report on Lunar Nomenclature by the Working Group of Commission 17 of the IAU". Space Science Reviews. 12 (2): 136–186. Bibcode:1971SSRv...12..136M. doi:10.1007/BF00171763. S2CID122125855.