I do not intend to address the complete history of literary realism or realism in general. The focus of this website is modern literary realism, i.e. literary representations of reality from the beginning of the nineteenth century to the present day. Literary representations of reality have been around for considerably longer than that. It is, however, from the nineteenth century onwards that we see the emergence of a specific genre.
For an excellent and well-written account and assessment of the greater history of realism, please consult Erich Auerbach's work, Mimesis, on the evolution of the representation of reality.
What I do want to stress in this overview are the principle changes and developments within the genre and the evolution in the attitudes to truth, humanity and reality and their representation.
Erich Heller differentiates between two major periods within modern literary realism. The first is the works of the nineteenth century; the second from the beginning of the twentieth century (595). I shall follow his lead and respectively refer to this division as early and late literary realism.