While the Muskingum Genealogy Society's library is probably the first place people look for reference material on Muskingum County, there are many other archives and libraries in and out of Ohio that might prove useful in finding information on the County and it's residents.
Muskingum County Chapter of the Ohio Genealogy Society (MCCOGS) Archives
MCCOGS
P O Box 2427
Zanesville, OH 43702-2427
Location: Second floor of the John McIntire Library
Website: http://mccogs.org/
Ohio Historical Society Archives/Library
1982 Velma Ave.
Columbus, OH 43211
Website: http://www.ohiohistory.org
Ohio State University Archives
2700 Kenny Road
Columbus, Ohio 43210-1046
Tel: 614) 292-2409 or (614) 292-1767 (Photo Archives)
Fax: (614) 688-4150
Hours: M-F: 9:00 - 12:00 and 1 - 4:30
Website: http://library.osu.edu/find/collections/the-ohio-state-university-archives/
Ohio University Archives and Library
Ohio University
Athens, Ohio 45701
Tel: 740-593-2699
Website: https://www.library.ohiou.edu/archives/mahn/index.html
National Archives and Records Adminstration
Main Archive
National Archives and Records Administration
700 Pennsylvania Avenue, NW
Washington, DC 20408
Customer Service: 1-866-325-7208
Website Home: http://www.access.gpo.gov/nara/
Website Archives: http://www.archives.gov/
Muskingum County Library
John McIntire Library
220 North Fifth Street
Zanesville, OH 43701
Tel: 740-453-0391
Fax 740-455-6357
Website: http://www.muskingumlibrary.org
Online Catalog: http://66.213.91.5/
Ohio University-Zanesville Branch Campus Library
1425 Newark Road
Zanesville, OH 43701
Tel: 740-453-0762
Fax: 740-453-6161
Website: http://www.zanesville.ohiou.edu/library/zanesvill.html
Ohio State University Library
Main Library
1858 Neil Avenue Mall
Columbus, OH 43210-1286
Tel Main Library Reference: 614-292-6175
Website: http://www.lib.ohio-state.edu/
Daughters of the American Revolution Library
DAR Library & DAR Museum
1776 D Street, NW
Washington, D.C. 20006-5303
Tel: 202-628-1776
Email
Website: http://www.dar.org/library/