1833 citizens of Clarke County, Ohio FamilySearch Library
20th Century History of Springfield and Clark County, Ohio and Representative Citizens Internet Archive 
20th century history of Springfield, and Clark County, Ohio : and representative citizens FamilySearch Library
A Biographical Record of Clark County, Ohio Internet Archive
A Biographical Record of Clark County, Ohio, 1902 (included in U.S. County and Regional Histories and Atlases collection) Ancestry
A Biographical record of Clark County, Ohio FamilySearch Library
A Sociological Study of Clark County, Ohio Google Books
A Sociological Study of Clark County, Ohio Open Library
A standard History of Springfield and Clark County, Ohio Google Books
A standard history of Springfield and Clark County, Ohio: an authentic narrative of the past, with particular attention to the modern era in the commercial, industrial, educational, civic and social development FamilySearch Library
Abstracts from history of Clark County (Beers 1881) Ohio FamilySearch Library
Clark County History Index 1902 Heritage Pursuit
Clark County History Index 1922 Heritage Pursuit
Compilation of Published Sources MyHeritage
Early Clark County, Ohio families, vital statistics. Index of fathers of the family unit in volumes I through VII WorldCat
Early Clark County, Ohio families, vital statistics. Index of fathers of the family unit in volumes I through XI WorldCat
Historical and genealogical records of West Central Ohio FamilySearch Library
History of Clark County, Ohio, 1817-1889 : excerpted from the centennial history of Ohio; 1898 edition of Howe's historical collections of Ohio, and illustrated with sketches from 1846-1890 FamilySearch Library
Index to the history of Clark County, Ohio FamilySearch Library
Index, Yester year in Clark County, Ohio, volumes 1 thru 6 published by the Clark County Historical Society, 1947 through 1972 FamilySearch Library
Morgan Index of Ohio People, Businesses and Institutions, 1796-1850 (index of names that appear in many books, pamphlets and broadsides) OhioLINK
Periodical Source Index (index to 3.1 million articles in historical and genealogical publications) Allen County Public Library
Portrait and Biographical Album of Greene and Clarke Counties, Ohio, 1890 (included in U.S. County and Regional Histories and Atlases collection) Ancestry
Portrait and biographical album of Greene and Clark counties, Ohio : containing full page portraits and biographical sketches of prominent and representative citizens of the county; together with portraits and biographies of all the presidents of the United States FamilySearch Library
Portrait and biographical album of Greene and Clark counties, Ohio, containing full page portraits and biographical sketches of prominent and representative citizens of the county; together with portraits and biographies of all the presidents of the United States LDS Genealogy
Portrait and biographical album of Greene and Clark counties, Ohio, containing full page portraits and biographical sketches of prominent and representative citizens of the county; together with portraits and biographies of all the presidents of the United States Internet Archive
The History of Clark County, Ohio : a History of the County, its Cities, Towns, General and Local Statistics Ancestry
The History of Clark County, Ohio : containing a history of the county, its cities, towns, etc.; general and local statistics; portraits of early settlers and prominent men; history of the Northwest Territory; history of Ohio; map of Clark County; constitution of the United States, miscellaneous matters, etc., etc. FamilySearch Library
The History of Clark County, Ohio : containing a history of the county; its cities, towns, etc.; general and local statistics; portraits of early settlers and prominent men; history of the Northwest Territory; history of Ohio; map of Clark County; Constitution of the United States, miscellaneous matters, etc., etc. FamilySearch Library
The History of Clark County, Ohio, 1881 (included in U.S. County and Regional Histories and Atlases collection) Ancestry
The history of Clark County, Ohio, containing a history of the county; its cities, towns, etc.; general and local statistics; portraits of early settlers and prominent men, V. 1 LDS Genealogy
The history of Clark County, Ohio, containing a history of the county; its cities, towns, etc.; general and local statistics; portraits of early settlers and prominent men, V. 1 Internet Archive
The history of Clark County, Ohio, containing a history of the county; its cities, towns, etc.; general and local statistics; portraits of early settlers and prominent men, V. 2 LDS Genealogy
The history of Clark County, Ohio, containing a history of the county; its cities, towns, etc.; general and local statistics; portraits of early settlers and prominent men, V. 2 Internet Archive
Yester year in Clark County FamilySearch Library