Allegan sent most of their old records to the WMU Archives and Regional History Collection in Kalamazoo, MI. I think some records were lost or disposed of, or haven't been indexed yet at the archive, but your best bet would be to contact them. http://www.wmich.edu/library/archives/index.phphttp://www.wmich.edu/library/archives/index.php
Another place to check would be the Archives of Michigan in Lansing. Good luck with your search.