Answer
Typically, "historicism" is not an eschatological system but rather an approach to interpreting the central chapters of Revelation (especially chapters 6-18). The historicist approach reads prophecy as an outline of (church) history from the first century to the second coming. Historicism does not restrict itself to any particular view of the millennium - pre- post- and amillennialists may all be historicists.
Answer by Ra McLaughlin
Ra McLaughlin is Vice President of Finance and Administration at Third Millennium Ministries.