The Collaborative International Dictionary of English v.0.48:

Historically \His*tor"ic*al*ly\, adv.
   In the manner of, or in accordance with, history.
   [1913 Webster]

WordNet (r) 3.0 (2006):

historically
    adv 1: throughout history; "historically they have never
           coexisted peacefully"
    2: with respect to history; "this is historically interesting"

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "historically":
   actually, aforetime, before, before now, beforetime, certainly,
   earlier, erenow, erewhile, erst, factually, formerly, forsooth,
   heretofore, hitherto, in fact, in reality, in the past,
   in times past, in truth, in very sooth, indeed, indeedy,
   nothing else but, of a truth, only yesterday, prehistorically,
   previously, priorly, really, really-truly, recently, then, truly,
   undoubtedly, verily, veritably, whilom, with truth, yesterday