I use census records a lot. In fact, I really like looking through the old census records, although trying to locate someone in the census using an on-line index can be frustrating. Some of the surnames are nearly unrecognizable the way they are spelled and indexed on a website like Ancestry.com, the website I use the most for census research. I can’t blame them. Someone just transcribed the surname the way it was spelled on the census record. That is why, in my footnotes, I use the indexed spelling of a name, so it can be found in the on-line index.
If I cannot find a family using the on-line index I usually read through the whole township, line by line. That is actually interesting and a good way to familiarize myself with all the families and names in the township. It reminds me of the old days, before census images were indexed, digitized, and put on the Internet. In the old days I would go to a library and look through census records on microfilm, line by line, because they were not indexed back then.
I have been searching in vain for a family in the 1850 census, a family who likely lived in Black Creek Township.
While looking for them, reading through the 1850 census of Black Creek Township line by line, I noticed something very interesting. Something I have read about but have never found myself in a local census.
A family was enumerated twice in Mercer County, Ohio. I have read that finding duplicate entries of a family in the census is a bonus because you may learn some additional information. What a treat!
In 1850 Census Day was 1 June 1850. Census takers were given five months to take the census. The population of the United States was 23.2 million and the population of Ohio was a little over 1,980,000.
The 1850 Federal Census is an important census because it is the first census that listed the name of every person in the household. Before that only the head of the household was listed and other members of the household were marked in age categories by gender. The 1850 census provides other valuable information as well: age [on census day]; sex; color; birthplace; occupation; value of real estate; whether married within the previous year; whether deaf, dumb, blind, or insane; whether a pauper; whether able to read or speak English; and whether the person attended school within the previous year. Unfortunately, the 1850 census did not report family relationships within the household.
So who was the family enumerated twice in 1850, listed in both Black Creek and Dublin Townships?
Christian Hardzog [aka Hartzog] and his family were enumerated twice in the 1850 census, enumerated in both Black Creek Township and Dublin Township. It is rather easy to miss because the surname is written poorly in both enumerations. The name looks like and is indexed on Ancestry.com as Hartsey in Dublin Township and like Kartrong in Black Creek Township. I probably would not have noticed the double entry had not the names of the family members been familiar to me because I have been researching this family.
Below is how they are indexed on Ancestry.com:
Black Creek Township, enumerated 16 September 1850 by Vincent Bebout:
Wm, 3mOH 
The next day the Christian Hardzog family was asked the same questions by a different census taker. A couple of ages were reported differently and perhaps a different family member answered the questions the next day. Otherwise, the same person may have wondered why they were being questioned again. Elizabeth was Christian’s second wife and the King children listed were from her first marriage. I wonder if Elizabeth talked to the census-taker in Black Creek, since the King surname was given in the Black Creek enumeration and not in the Dublin enumeration. Also, it appears Sarah, 15, male (Dublin) is actually Noah, 16, male (Black Creek). I believe the indexer misread the name as Sarah, as it is nearly illegible.
Dublin Township, enumerated 17 September 1850 by Willshire Riley:
Wm, 3mOH 
I believe I know how the Christian Hardzog family came to be enumerated twice. I looked at both the 1850 census and the 1853 plat maps, comparing the families who were enumerated with the names of the 1853 landowners. By looking at the order in which the families were enumerated, it appears the census taker started in Section 1 of the township and went to Section 2, Section 3, etc.
Section 1 in Black Creek Township borders Section 6 in Dublin Township. George Hardzog is listed as the landowner in Section 1, Black Creek, in 1853. That appears to be where Christian and his family lived. In the census Christian Hardzog is listed with the families in Section 1, Black Creek and with the families in Section 6, Dublin.
The Dublin Township census-taker probably didn’t know exactly where the township line was and went into Black Creek Township and enumerated the family twice.
Just for the heck of it, since the Hardzogs lived so close to Willshire Township in Van Wert County, I read through that township, too. That would be something if the family was enumerated 3 times in one census! But no, I did not find them in Willshire Township. I guess their census taker did not cross the county line. Or perhaps the Hardzogs grew tired of answering the same census questions over and over.
In the end, this family was enumerated twice but I still have not found the family I was looking for in the first place. It appears they were not enumerated even once in 1850!
 1850 U.S. Census, Black Creek, Mercer, Ohio, p.288B, dwelling 34, family 35, Christian Kartrong; Ancestry.com (https://www.ancestry.com/search/collections/8054/ : viewed 24 Mar 2021).
 1850 U.S. Census, Dublin, Mercer, Ohio, p.276A, dwelling 803, family 807, Christian Hartsoy; Ancestry.com (https://www.ancestry.com/search/collections/8054/ : viewed 24 Mar 2021).