The Collaborative International Dictionary of English v.0.48:

Whereas \Where*as"\, adv.
   At which place; where. [Obs.] --Chaucer.
   [1913 Webster]

         At last they came whereas that lady bode. --Spenser.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Whereas \Where*as"\, conj.
   [1913 Webster]
   1. Considering that; it being the case that; since; -- used
      to introduce a preamble which is the basis of
      declarations, affirmations, commands, requests, or like,
      that follow.
      [1913 Webster]

   2. When in fact; while on the contrary; the case being in
      truth that; although; -- implying opposition to something
      that precedes; or implying recognition of facts, sometimes
      followed by a different statement, and sometimes by
      inferences or something consequent.
      [1913 Webster]

            Are not those found to be the greatest zealots who
            are most notoriously ignorant? whereas true zeal
            should always begin with true knowledge. --Sprat.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "whereas":
   albeit, although, as, as far as, as long as, as things go,
   at which time, because, being as how, boundary condition, catch,
   cause, clause, condition, considering, donnee, during which time,
   escalator clause, escape clause, escape hatch, fine print, for,
   forasmuch as, given, grounds, howbeit, in that, inasmuch as,
   insofar as, insomuch as, joker, kicker, limiting condition, now,
   obligation, parameter, parce que, prerequisite, provision,
   provisions, proviso, requisite, saving clause, seeing,
   seeing as how, seeing that, since, sine qua non, small print,
   specification, stipulation, string, terms, the while, ultimatum,
   when, while, whilst



Bouvier's Law Dictionary, Revised 6th Ed (1856):

WHEREAS. This word implies a recital, and in general cannot be used in the
direct and positive averment of a fact in a declaration or plea. Those facts
which are directly denied by the terms of the general issue, or which may,
by the established usage of pleading, be specially traversed, must be
averred in positive and direct terms; but facts, however material, which are
not directly denied by the terms of the general issue, though liable to be
contested under it, and which, according to the usage of pleading, cannot be
specially traversed, may be alleged in the declaration by way of recital,
under a whereas. Gould, Pl. c. 43, Sec. 42; Bac. Ab. Pleas, &c., B. 5, 4; 2
Chit. Pl. 151, 178, 191; Gould, Pl. c. 3, Sec. 47.