Tertiary sources in genealogy

You can roughly group all genealogical sources into three types: Primary, Secondary and Tertiary.

In this video, I’m going to give a quick, five-minute overview of tertiary source documents, which are summaries of family research without supporting citations. Quick version: assume good intent, but know the author made mistakes. You should use their research as a roadmap to find their sources, and double-check every part of their work.

You can roughly group all genealogical sources into three types: Primary, Secondary and Tertiary.

Primary source documents are created contemporaneously with a given event. Secondary source documents are detailed analyses written after the event—sometimes centuries after—and are based on explicitly cited primary source documents.

When I review tertiary sources, I follow my principles for genealogy research. First, the person who created the source had good intentions. They’re not lying, they’re not fabricating facts out of thin air. They want to get this right. Second, despite their best efforts, they’re human. They make honest mistakes. They might have misunderstood the record, confused it with another person, or even presented a guess from another researcher as fact.

To put it another way, you shouldn’t trust tertiary sources to have the facts correct, but you can use them to retrace someone else’s steps to help speed up your search.

Let’s look at two examples of tertiary sources.

First, the genealogy of Jacob Esher Heyl contained in Colonial and Revolutionary Families of Pennsylvania, and published by the Historical Society of Pennsylvania in 1911. I was specifically interested in Philip Heyl, an ancestor of my wife and a Philadelphia baker who fought at the Battle of Princeton in January of 1777. The source gives his birth and death dates, and that’s enough to find a primary source noting his date of death, as well as a will which proves his connection to the Raser family.

Let’s take an example where assuming good intent will lead you astray: Eugene Singer’s “A Singer Family of Colonial Vermont and Canada.” First self-published in 1996, Singer’s work was the only published genealogy of the George Slough who married and had a family in Pennsylvania in the late 1700s, and died in Ontario, Canada around 1811.

Singer asserted that George Slough was the eldest son of J. Philip Schlauch and A. Margaretha Hertzel of Northampton County, Pennsylvania—their son was of the right age and came from Pennsylvania.

Philip died intestate in the 1750s, and the Orphan’s Court record notes that their eldest son, George, made claim to the estate in 1759. Singer wrote that in 1769, George’s younger brother, “Jacob Slough petitioned the court for division of their father’s estate. It is a matter of record that George did not participate in this event.” Singer then writes that the genealogy upon which he relied states that “George had ‘probably died’ since there was no further record.”

At point, Singer’s genealogy goes a bit pear-shaped, and he alleges that George Slough didn’t really die, he was just presumed dead by the Orphan’s Court. Singer says that George had just “moved out” because of his wicked stepfather, and was living seventy-miles away in Berks County, Pennsylvania.

Singer’s work gives you a roadmap to retrace his steps, and the directions point to Hannah Benner Roach’s 1966 genealogy of the Herzel family published in the Pennsylvania Genealogical Magazine. I found that article on Ancestry.com, and it notes that Philip Schlauch & Margaret Hertzel’s son George “died unmarried and without issue.”

Taking it a step further, I found Philip Schlauch’s probate record on familysearch.org, where the contemporary record notes that “George the eldest son (who died since without Iʄsue).”

Let’s assume good intentions: Singer found Roach’s article in the 1980s or early 1990s, mis-wrote his notes, and came to the wrong conclusion. But he provided enough information in his work to retrace his steps. And with that I could conclude that he made a mistake. There were two men name George Slough of about the same age living in Pennsylvania. One died around 1760, the other moved to Canada and died in 1811.

The George Slough who died in Canada was probably born in Germany, and considering how many George Sloughs there were in Colonial Pennsylvania, it can be tough to separate them out.

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