The records of Moselem Church note the 1756 marriage of Johannes Mertz and Rosina Haffa and say that Johannes, a wheelwright, was the son of Johannes “aus dem Wurtenburgishem Stochenhausen” (from Stockhausen in Wurttemberg, Germany). That record was written by the minister who married this couple and I have seen other similar citations for immigrants which named the father back in Germany and I have no reason to think it wrong.

Now there are some people who state in their family trees that John Henry Mertz, founder of Mertz Church, was from Stockhausen. For example, my father’s cousin who did his genealogy in about 1970 told me, mistakenly, that I was descended from John Henry and he also told me, mistakenly, that John Henry came from Stockhausen. (When I later went to Germany and asked German friends where Stockhausen was, they said it just means “a village” as opposed the name of a particular village.)

But the truth is the record says that about Johannes and only Johannes. So either people totally misunderstood that fact or they assumed that John Henry was a brother to Johannes. But that can be ruled out since we now know the name of John Henry’s father (it was not Johannes) and the names of his brothers (there was no Johannes) and where John Henry was from (it was not Stockhausen).

It is a fact that Johannes, John Henry and Jost all worshipped at Mertz Church at some time and that seems to be where they all started out in the new world. Later, they and some of their descendants migrated from there. So, they may have been related, for example cousins of some sort. If we could ever find a known descendant of Johannes, then his DNA could prove whether or not John Henry and Johannes were related or not. Until then, I just don’t know.

Johannes gets the single letter designation J. He is one of the five Mertz “original American ancestors” who settled in Berks County. The other three “original American ancestors” settled elsewhere.

Johannes and Rosina were named twice in the records of Oley Reformed too, as sponsors, in one case for a son of Christoph Gerhard in 1764 and the other for the son of Johannes Friederich and wife Eva in 1766. It is curious their associations at times with Mertz Church, at times Moselem and at other times with Oley and also interesting that their marriage was recorded at both Moselem and Mertz Church.

Johannes and his male descendants to 1850 are covered in the Mærtz Hierarchical Project:
https://www.mertzgenealogy.com/names/johannes_mertz_family_j.pdf

The thing I don’t know for certain is whether Johannes was the immigrant of that name who came in 1749 or was instead the immigrant listed as Hans Martz who came in 1751. I had always thought Johannes was the 1749 immigrant as that is what Morton Montgomery said but then I read a published family history that mentioned Johannes (the one associated with Mertz Church) as the other guy -- Hans in 1751. I consider neither source authoritative and will simply say I don’t know which was Johannes (though I still lean to the 1749 guy) but it really doesn’t matter. We’re discussing here the Johannes associated with Mertz Church. I think he arrived 28 Sep 1749 on the ship Ann.

In the Annals of Berks County, Montgomery tells the story of Johannes Mertz. He was the son of Johannes of Stockhausen, Wurttemberg. He emigrated in 1749 and married Rosina Hase daughter of Melchior in 1756. Their children were Johannes 1757, Anna Maria 1760, Maria Salome 1763, Melchior 1765 and Peter 1769.

The estate of John Mertz, wheelwright of Maxatawny, entered administration 13 May 1773 with Rosina the widow as administrator. (Her sureties were from Maxatawny Township, Oley Township and Reading). I have examined his estate file, unfortunately there are no clues as to the names of his children.

Several of the early sources many people have relied on when researching their Mertz ancestry clearly imply that Johannes is the “key immigrant” of the Mertz family in America.

J L Floyd called him “the founder of this family in America” while Joseph A Meiser amended that description and said Johannes’ father, who did not emigrate was “the progenitor of several of the Martz (Mertz) families in America” (i.e. several of the other immigrants were thought to be brothers of Johannes) and both of those sources said “the church located near his home was named Mertz Church in his honor”.
All those statements are wrong!
• Johannes was only one of the eight early immigrants I have identified. In terms of known descendants, he has about the fewest of these eight immigrants.
• I can absolutely declare that two of the other immigrants were not related to him in any way, two others were definitely not his brothers (though may have had a more distant relationship to him) and I think it unlikely the other three were related to him in any way. I think his father was the progenitor of just Johannes and his descendants, no one else.
• Mertz Church was named for a different immigrant, John Henry Mertz. Johannes came to America after the church was founded — on land donated by John Henry. Johannes did baptize several children in that church but his family was not nearly so prominent in their early records as John Henry’s.
• A Berks County deed clearly records the fact that John Henry Mertz donated the land for Mertz Church. The recording of baptisms at that church began in 1749 but the first page of the register lists all of John Henry’s children baptized prior to 1749. He was the only church member for whom there was such a “catch-up” list. He was clearly considered the founder and that church was clearly named in honor of him.

We know his two daughters from their baptisms:

Anna Maria was born on 2 Dec 1760. Maria Salome was born on 24 May 1763.

[As an aside, in the records of Rev Stoever, there is record of the birth of Maria Barbara Mertz in 1751 daughter of Johannes of (or at) Northkill. It is not at all clear who this Johannes was -- another immigrant or this Johannes with a first wife prior to Rosina?]

We know for sure two sons of Johannes from their baptisms:

J1 Johannes was born on 17 Jul 1757 and baptized at Moselem.

J2 Melchior was born 11 Apr 1765 and baptized at Mertz Church. His is a unique name in the Mertz families, he was named after his wife’s father.

Many sources -- including Morton Montgomery and Charles A Fisher -- that were often accurate, though sometimes had errors -- add a third son:

J3 Peter, born, supposedly, 9 Mar 1769. There does seem to have been such a man, I know something about him and otherwise I do not know who he was but I have never seen the absolute proof that he was the son of Johannes. There was no record of Peter’s baptism that I have found. However, I include him here as his third son.

Of the five Berks County Mertz immigrants, Johannes is the only one that I worry may have had a son I haven’t yet identified. I think he had just those three sons but I’m not 100% certain. If I totally believed Morton Montgomery, I would conclude that these were his only three sons, I just have to leave open the possibility that maybe there was another one no one knows about.

Rosina Mertz is on find-a-grave, buried in Alsace Manor. I don’t know who else it could be other than this Rosina.