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Don’t Trust Derivative Records for Genealogical Research

An extreme statement, but now that I have your attention, let me tell you this cautionary tale about what a difference a letter can make to your research when there’s a small transcription error.

A derivative record is created from an original document by transcription, translation, or reproduction to expand accessibility to its information.[1] Examples of derivative records include indexes, abstracts, lists, and summaries. They save time with our research by letting us quickly locate information that is often more legible and organized than the original.

I was reminded of the title’s “extreme” warning just this past month while reviewing a transcript of 18th century marriages from Old Swedes Church in Philadelphia, Pennsylvania. On, I found the following derivative record created by the Pennsylvania Archives, which was printed nearly a hundred years later in 1876.

I was researching John McMasters, who married Elizabeth Boxon on 12 October 1782 when I noticed that 10 days later a Margaret McMasters married John Fanighans on October 22. At this point in time in Philadelphia, the McMasters surname was not too common, and I wondered if Margaret could be a sister of John. I only knew one other sibling for John and was unsure who his parents were. So, the opportunity to explore another sibling’s documentary life, which might lead to other evidence for John’s parents, was irresistible. 

Searching For Margaret Fanighans

From my past Irish research, I knew that names like Fanighans were often spelled differently from record to record due to illiteracy and accents for some Irish. Consequently, recorders often spelled these names phonetically. Indeed, one of my Irish lines adopted the spelling of Minnigan in the late 1800s, but I have found records where it was spelled Minehan, Manahan, and many other derivatives. In Ireland, the currently accepted spelling of it is Meeneghan or Meenaghan.

I searched for John and/or Margaret Fanighans in the Philadelphia and broader Pennsylvania area in the late 1700s and early 1800s and found nothing. Searching for the alternate spellings of Fanighans, I found a 1773 indentured servant document in Philadelphia for John Finnigan and a reference to a widowed Margaret Fenegan in the 1790 census in Allegheny County, Pennsylvania as well as Margaret Feanigan in a 1797 church record in Lancaster County, Pennsylvania. 

None of the records appeared connected to one another or provided a reasonable and consistent timeline. My genealogical gut was telling me something was off. I’ve written about the dangers of derivative records previously (see Genealogical Indexes: Friend or Foe and The Power of Original Records). So, I began to search for the original marriage records rather than rely on the derivative records.

The Original Records

In the search for the original records, I checked both and the website for the Old Swedes Church. Records on FamilySearch were only viewable at a Family History Center, and the Old Swedes Church’s website offered no obvious research assistance with its archives. I opted to visit the Family History Center, which is only open a couple of times of week. In the age of instant gratification with online records, waiting three days to visit the Center was a test of patience.

Once at the Center, I quickly located the record group, but the actual film for the marriage records was not obvious.[2] The 1782 marriage was not found in the film titled “Baptisms 1879-1927 – Marriages 1750-1789” but instead in the film titled “Church Records 1636-1789”. As if taunting my patience and perseverance, records were organized by officiant rather than one large chronological book.

Taking stock of the process in locating the original record, I can see why some hesitate or never take the extra step to do this, but here is what I found:

In the original record, John Fanighans’ name was actually spelled with an “L” – Flanighans. Phonetically, from a search bar perspective in or, Fanighans and Flanighans produce very different results, which is perhaps why my initial search results didn’t feel right. 

Beyond the search results differences, Flanighans and Finighans are entirely different surnames. According to the House of Names, Flanagan and Finigan both originate from the West of Ireland but have very different meanings.[3] Flanagan is derived from the Gaelic word flann, which means red or ruddy while Finigan is derived from fionn, which denotes a fair-headed person. Ironic that both surnames reference very different color profiles reinforcing the difference a single missing letter can make.

A New, Informed Search

Armed with a more accurate reading of the original record, I “quickly” found John Flannagan in the 1790 U.S. census living as a porter on Plumb Street in the Southwark district of Philadelphia.[4] While I did not find Margaret (McMasters) Flannagan’s hopeful brother, John McMasters, in the 1790 census, I did find John McMasters living at 44 Plumb Street in the 1793 Philadelphia City Directory and John Flanaghan living at 22 Plumb Street.[5] The directory listed John McMasters as constable and John Flanaghan as a porter. Geographically, there was a connection.

While I have not yet fully constructed the proof argument proposing that Margaret (McMasters) Flanagan is John McMasters’s sister, I have made a good start with this discovery. More importantly, because I obtained a copy of the original record, I avoided the often too common trap in traveling down the rabbit hole investigating the “wrong” ancestor. What a difference a letter can make!


So, should we trust derivative records? Of course, but with an understanding of their limitations.

My experience is that a majority of transcriptions are correct, and derivative records save genealogists time. In fact, derivative records have helped me to break down many brick walls by pointing to records and information I may not have otherwise discovered on my own. However, as this cautionary tale afirms, if we find a derivative record seemingly important to our research, obtain a copy of the original record. It could save you even more time and be even more helpful.

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[1] Jones, Thomas W. (2013). Mastering Genealogical Proof. Arlington, VA: National Genealogical Society.

[2] Gloria Dei Church, Swedes Church, Philadelphia, Pennsylvania, John Flanighans and Margaret McMasters (22 Oct 1782), Church Records 1636-1789, Film 511804, Image Group Number 8104381, image 623 of 658.

[3] Swyrich Corporation (n.d.). Finigan History, Family Crest & Coat of Arms and Flanagan History, Family Crest & Coat of Arms, accessed 30 October 2022 at 

[4] 1790 U.S. census, Philadelphia County, Pennsylvania, population schedule, Southward, p. 364, image 9 of 66, Jno (Porter) Flannagan; database with image, Ancestry (, accessed 1 November 2022); Family History Library Film 0568149.

[5] City Directories for Philadelphia, Pennsylvania, John Flanaghan (1793), p. 46 and John McMasters (1793), p. 95, T. Dobson Publishers; database with image, Fold3 (, accessed 1 November 2022).


Published by Rick T Wilson, PhD

As the Family Pattern Genealogist™, I detect and analyze patterns in genealogically relevant data using DNA and other traditional records.

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