In February 1820 the Ohio government authorized the establishment of Mercer County and Van Wert County. Mercer County was organized in 1824 and Van Wert County was organized in 1837. St. Marys Township, now part of Auglaize County, was organized in 1824 as part of Mercer County. Auglaize County was established and organized in 1848 from Mercer and Allen counties. 
During this same general time period the village of Willshire was platted by Captain James Riley in 1822. Yes, this year Willshire celebrates its Bicentennial.
I have been looking at the earliest census reports for this area and wondered who the earliest settlers in this area were.
Since neither Van Wert nor Mercer County were organized in 1820, they are not among the 57 Ohio counties searchable in the 1820 census on Ancestry.com. However, 18 persons were enumerated in “Mercer County” in 1820. “Mercer County” was included with Darke County’s 1820 census enumeration. Darke County was established in 1809 and organized in 1817, several years before Mercer County.
1820 census enumeration of Mercer County, Ohio:
Anthony Shane 
Column no.3 in the 1820 census asked the number of males age 16-18 and column no.4 asked the number of males age 16-26. Males in the 16-18 age group would also have been listed in the 16-26 age group but were not supposed to be added twice in the final count. Counting all the marks could account for the total number of children not matching your family records or other records. John Roebuck had the only male in the 16-18 age group.
I compared the above 1820 list with the those enumerated in Mercer County’s 1827 Quadrennial Enumeration. This gives me an idea where in Mercer County some of these individuals were living 7 years later, although some may have moved or passed away. Those from the 1820 census who were still in Mercer County in 1827 were all living in Dublin Township. This is not a surprise because Shanesville, the oldest town in Mercer County and now called Rockford, was established in 1820 by Anthony Shane and is in Dublin Township. Note that Anthony Shane was enumerated in Mercer County’s 1820 census.
Mercer county 1827 Quadrennial Enumeration:
Calvin Dennison [likely the Calvin Drimeston in 1820]
There were 2 others with the same surname but a different given name:
John Lillie [may be from the Abitha Lilly household?]
Timothy Greene [may be from the Abner Greene household?] 
You might wonder what a Quadrennial Enumeration is. Per Ohio’s 1802 State Constitution, every 4 years Ohio counties were to take an enumeration of white males over 21 years of age. The censuses were taken for legislative apportionment but were often mistaken as tax lists because tax assessors from each county were in charge of the count. These enumerations were taken from 1803-1911.
Over 1800 Quadrennial Enumerations were taken in Ohio but fewer than 100 survive. Mercer County’s 1827 and 1843 Quadrennial Enumerations have survived and the 1827 is the earliest known to exist for the county. The original documents are housed at the Paul Lawrence Dunbar Library Special Collections and Archives at Wright State University, Dayton, Ohio. The Mercer County Chapter of the Ohio Genealogical Society photocopied and transcribed the 1827 and 1843 lists in 2004.
Next, I compared both above lists with Mercer County’s 1830 census, to see where the same people were living.
Mercer County, 1830 census enumeration:
Isiah Dungan-St. Marys Twp
Benjamin Roebuck-Union Twp
John Roebuck-Dublin Twp
Samuel Hanson-Union Twp
Ruel Roebuck-Dublin Twp
Michael Harner-Union Twp
John Lillie-Dublin Twp
Timothy Green-Dublin Twp
Another interesting thing is that Willshire Township is listed with Mercer County in the 1827 Quadrennial Enumeration. The source I have shows three townships in the 1827 Quadrennial Enumeration: Dublin, St. Marys, and Willshire Township (Van Wert County). I do not know if Willshire Township was originally grouped with Mercer County or if it was added to the publication because of its proximity to Mercer County. At any rate, since Willshire was not organized until 1837 and was not included in the 1830 census, this is one of the earliest lists of inhabitants of Willshire Township:
Willshire Township, 1827 Quadrennial Enumeration:
Peter Bolenbaugh Senior
Good information from census enumerations.
 County Establishment: Until a county was formally organized it remained attached to its parent county or surrounding counties. County Organization: A county did not function as a county until it was organized. It is possible a land-owner never moved, yet various records may show he had different counties of residence.
 1820 U.S. Census, Richland, Darke, Ohio, p.168; Ancestry.com, viewed 28 Jul 2022.
 1827 and 1843 Quadrennial Enumeration of Adult White Males of Mercer County, Ohio, The Mercer County Chapter of the Ohio Genealogical Society, 2004, self-published.