landmark (n.) Look up landmark at
Old English landmearc "object set up to mark the boundaries of a kingdom, estate, etc.," from land (n.) + mearc (see mark (n.1)). General sense of "conspicuous object in a landscape," originally especially one that can be seen from sea, is from 1560s. Modern figurative sense of "event, etc., considered a high point in history" is from 1859.