It is worth noting that the Schoen and Bleed reference suggested by Veit is
to be found in Central Plains Archaeology, vol. 2, no. 1, available from
the Nebraska Assn. of Professional Archaeologists.  I can help you get a
copy if it is not available through your library.
 
I also have a vague recollection of one or more brick clamps being
excavated in Illinois several years ago, probably by Illinois State
University or Fever River Research (Springfield) for the Illinois Dept of
Transportation.  There should also be information in the state site files.
Possible contacts on brick making in Illinois include Floyd Mansberger, Joe
Phillippe, Mark Esarey, John Walthall, or Charles Orser, all of whom are in
the SHA membership list (June 1996 newsletter).
 
Lance K. Green, at Univ of Tennessee, Knoxville, published a 1992 paper
called "The Penfield is Mightier than the Sword: Machine-Made Bricks in
Knoxville and KNox County, Tenn." in Proceedings of the 10th Symposium on
Ohio Valley Urban and HIstoric Archaeology (Tenn Anthropological Assn, Misc
Papers, No. 16.
 
I do not have a full run of those proceedings, but I know that other papers
have been given that address brick making (though perhaps not subsequently
published).  I would suggest contacting Donald Ball or Philip DiBlasi, who
ran the conference for many years (again, listed as SHA members).
 
The Association for Preservation Technology put out a Bulletin in 1975 that
includes John Voltz's "Brick Bibliography" APT 7(4):38-49.
 
Also check cultural geographer William D. Walters, Jr.'s (1982) "Nineteenth
Century Midwestern Brick" in Pioneer America 14(3)125-136.  He is in the
Geography Dept at Illinois State and would be an excellent source on rural
industries such as brickmaking.  In fact, I believe he collaborated with
Mansberger on such an article.