Claude Duval LaCoste (1871–1926)

Claude Duval LaCoste in 1914. This was probably his wedding photograph for his second marriage to my great grandmother, LaPerle Elmer.


My Mawmaw (grandmother) lost her father when she was only 3. Her strongest memory of him was being held over his casket to kiss him goodbye, an experience that left her with an abiding fear of corpses. She preferred to focus on his life, and often recounted the tale of his immigration to America from Bergerac, France. He and his older brother Leopold “Paul” ran away from home as teenagers and hopped a ship to America. Paul contracted scarlet fever on board and died soon after arriving on Ellis Island, leaving 16-year-old Claude alone and penniless. Remembering his father mention a family friend named Coudron who’d settled in a small town in Louisiana, Claude decided to work his way down the coast to New Iberia, where he eventually met and married my great grandmother, LaPerle. Mawmaw later wrote this account for posterity:


There is only one problem with this narrative:  it’s not true.


The Mystery of the Records

Claude does not appear in any U.S. census records prior to 1900, lending credence to the immigrant story. On the other hand, he’s not listed in the Ellis Island records, nor is his brother. My cousin and genealogy mentor Bryan pointed me to a reference to a Claude LaCoste in Southwest Louisiana Records, an index of church and courthouse records by Father Donald Hebert. The listing was odd, though:  it says that child was born in 1871, but the church register referenced was from 1882.

This index record indicates that a child named Claude Dural (sic) LaCoste, son of Paul LaCoste and Marie Couyet, was born on 16 March 1871. The index cites the original record in the registers of St. Peter’s Catholic Church in New Iberia, Louisiana (NI Ch.), volume 4, page 10. That volume covers the year 1882, not 1871.


The birth day and month were the same as the one on Claude’s tombstone, but the year was off by two. Even so, I felt a twinge of excitement that I’d found his parents: Paul LaCoste and Marie Couyet. His father’s name agreed with my grandmother’s memory of a brother named Leopold, who went by Paul. Claude’s brother must have been a Junior.

Claude Duval LaCoste Sr., March 16 1873–May 30 1926


The next time I was in Louisiana, I visited St. Peter’s Church in New Iberia, where a volunteer was kind enough to photocopy the baptismal record in question.

Translation: On the 6th November, 1882, I the undersigned baptized Claude Duval, born on the 16th March 1871, son of Paul Lacoste and Marie Couyet. Godparents: N.D. Coudron and Sarah Sampson. -C. Jacquet


This had to be the right person; his godfather was Coudron!  Another piece of the puzzle fit into place.

But why was Claude not baptized until age 11?  Did the family live so far from a church that they didn’t see a priest for more than a decade? Had the family immigrated together and lost their records, requiring them to baptize Claude again? And if they’d lost Claude’s records, why hadn’t they lost Paul’s? Claude’s was the only LaCoste baptism on that on that date. Or was there some other reason not to baptize him, like illegitimacy?

On that visit to St. Peter’s, I also obtained the church record of Claude’s first marriage, in 1900. This one listed his parents as Leopold LaCoste and Mary Crouchet. It appeared that Leopold did go by Paul, and the different spelling of his mother’s surname was intriguing:  Crouchet or Crochet is a relatively common (non-Cajun) surname in southern Louisiana, but I’d never heard the name Couyet before.

Translation: The 1st of February 1900, after seeing the license from the Iberia court, and not knowing any impediment to the marriage, I the undersigned, G. M. Jouan, Curé of New Iberia, gave the sacrament of marriage to Claude Lacoste, legitimate son of Leopold Lacoste and of Mary Crouchet, and to Marie Etié, legitimate daughter of St. Cyr Etié and Camilla Labauve. The spouses and witnesses have signed with me below.


That seemed to rule out one possible explanation for the late baptism: the marriage record explicitly says that Claude was legitimate. Perhaps the family had come from France after all, but clearly Claude hadn’t run away from home, not if his parents were present at his baptism and first marriage.

My grandmother insisted that her father was from France until the day she died. Later, as my mother was going through Mawmaw’s papers, she discovered Claude’s death certificate. We already knew the story of his death. On 30 May 1926, he collapsed beneath an oak tree in front of the New Iberia high school on Center Street while on the way home from a baseball game. The weather was undoubtedly hot and humid, he had a chronic heart condition, and he was upset over a bad call by the umpire. He died in the ambulance on the way to the doctor. What we didn’t know was that the death certificate said that both Claude and his father were born in New Iberia, the same town where Mawmaw grew up. Claude had spent his whole life there. He wasn’t from France at all! And the death certificate confirmed that his mother’ surname was Crouchet, not Couyet.

Claude’s death certificate. Both he and his father were born in New Iberia, Louisiana.


If Claude was a local, why didn’t he appear in any censuses before 1900? And why couldn’t I find a Marie LaCoste in 1880 or 1900?  I found a 31-year-old man named Leopold LaCoste in 1880, a wheelwright living with his wife Euphemie and three children in Vermilionville, about 20 miles away. (The town was renamed Lafayette in 1884.) His oldest child, a girl, was 6 at the time. Claude was not a part of that household. Further investigation revealed that this Leopold had married Marie Euphemie Broussard on 3 April 1871. Documents don’t agree on the year of Claude’s birth (1871, 1872, or 1873), but if his baptismal record and death certificate are correct, Leopold married Euphemie just two and a half weeks after Claude was born.

In 1870, Leopold was living with his parents, A. LaCoste and Jane (Antoine LaCoste and Jeanne Salvan). Then 21, Leopold was already a wheelwright, and his father was a blacksmith. The family was listed on pages 11 and 12 of the Vermilionville census. On page 13 was a family headed by a woman named Mary A. Crouchet, and with an 18-year-old girl also named Mary. The girl Mary’s father, Jean (or John), had been a wagoner who had died of “coup de soleil” (sunstroke) less than a year before. A wheelwright and a wagoner’s daughter …

By this point, I was pretty sure that I’d found Claude’s parents, although the church record of his marriage to Marie Etié still bothered me.  It clearly stated that he was legitimate, which wasn’t possible if his father had married someone just else days after he was born (or worse, fathered him while already married to someone else).  I wanted to confirm my suspicions using DNA.


DNA Evidence for Claude’s Father

Claude had two children. His only son, Claude Jr., died while serving in World War II and left only an infant daughter. With no living male-line descendants, yDNA was not an option. His daughter’s daughter, my mother, had done an autosomal DNA test at AncestryDNA, where she had dozens of matches with the surname LaCoste in their trees, but most had no apparent connection to Leopold. Two, however, did: A.A. is his great granddaughter, and J.W. is the great grandson of Leopold’s sister, Marie. Thus, they would be half 2nd cousin and 3rd cousin, respectively, to my mother if I was right that Leopold was Claude’s father.

J.W. only shares 14 centimorgans (cM) of DNA with my mom, weak evidence for this particular connection at best. Mom and A.A., on the other hand, share 92 cM, which was promising. But A.A. is also buried near the bottom of Mom’s list of “3rd Cousins” at AncestryDNA, which spans two pages. That was less promising. See, my mom is Cajun, and Cajuns are endogamous; they have been marrying within a relatively small population since they arrived in Louisiana in 1765, and they were endogamous back in Acadia (Nova Scotia) before they were illegally expelled by the British in 1755. ALL Cajuns are cousins, multiple times over. Some of the “3rd Cousin” matches in my mom’s list really are in the 3rd cousin range, but many are not. That means A.A. and my mother could be related through another line—or multiple other lines—and not necessarily through Leopold.

Fortunately, Leopold’s parents were French, not Cajun, and A.A. has a fairly extensive tree with only one Cajun line, through Leopold’s wife, Euphemie Broussard. All of the Broussards in Cajun Louisiana are descended from one Acadian family, and a famous one at that. Joseph Broussard (1702–1765)—described in a 1755 census of refugees in Petitcoudiac, New Brunswick, as “Le famoux Beausoleil”—and his brother Alexandre (1699–1765) led the resistance to the British expulsion for a decade before taking an extended family group to Spanish Louisiana in 1765 to settle what is now called Acadiana. Other Broussards, sons of their brothers, arrived later. My family is descended from the Broussards at least three times.


1755 census record for Joseph Broussard, “the famous Beausoleil”, who led the first Acadians to Louisiana. A pdf scan of the census is available here. See page 7.


To be able to use the DNA match to A.A. as proof of Claude’s parentage, I needed to rule out the possibilities that the amount of shared DNA between Mom and A.A. was a fluke or that it could have come through Euphemie. First, I tested Claude’s two other grandchildren, my mother’s brother S., and Claude Jr.’s daughter C.L. The latter was especially important to my goal because her mother wasn’t from Louisiana, so her only ties to Cajun endogamy should be through Claude Sr.’s wife, LaPerle Elmer (my great grandmother and namesake). On her own initiative, A.A. also tested her sister, L.A., so I had another set of comparisons to consider.

Table showing the amounts of DNA shared between my three family members (Mom, Uncle S., and C.L.) and known descendants of Antoine LaCoste, Leopold’s father (A.A., L.A., and J.W.). The column on the far right shows the amount of shared DNA expected given the proposed relationship. The average is taken from the ISOGG wiki and the range (in parentheses) from the Shared cM Project.


The values all fit nicely within the expected range if Leopold was Claude’s father. Furthermore, the average segment sizes for most of the comparisons were relatively large.  Because DNA segments are whittled down in size through the generations, a few large segments indicate a closer relationship than many small segments, even when the total amount of shared DNA is the same.

Average segment sizes in the nine pairwise comparisons between my three close relatives (Mom, Uncle S., and C.L.) and the three known descendants of Antoine LaCoste (A.A., L.A., and J.W.).


The second strategy was to build back the tree for Euphemie at least four generations on all lines to look for alternate connections. By that point, her tree was starting to tie into the one I’d already built for my extended family. Ultimately, I didn’t find one or two connections between A.A. and my mom via Euphemie; I found 27! The closest was 6th cousins, and the furthest was 10th cousins once removed.

Could the 27 connections via Euphemie explain the shared DNA between the A.A. and my mom? I don’t think so, for two reasons. First, if I add up the expected amount of shared DNA for all 27 relationships, I get a total of only 1.4 cM. The average amount shared between my mom and her brother on one hand and A.A. and her sister L.A. on the other is 100.5 cM. Furthermore, the expected amount of shared DNA for between C.L. and the two sisters is only 0.9 cM, whereas the actual amount shared averages 78 cM. (Recall that C.L. has no Cajun on her mother’s side.)

The second reason I don’t think the shared DNA could have come solely though Euphemie is that the segments are too large. AncestryDNA doesn’t provide information on individual DNA segments, but they do tell us the total amount of shared DNA and the number of segments. Uncle S. shares 115 cM of DNA across 5 segments with L.A., for an average of 23 cM per segment. The largest segment in that comparison is probably longer than that, but it can’t be shorter. I calculated the probability that a single segment of 23 cM could survive the 13 transmission events between 6th cousins, the 15 transmission events between 7th cousins, etc., then added up all of the probabilities.  The chances that Uncle S. and L.A. could share a single 23-cM segment through Euphemie is 8.01 x 10^–6, or about 1 in 124,852. This statistic is an underestimate of the true probability because the longest segment is certainly longer than 23 cM and it doesn’t account for the other shared DNA.

Q.E.D.: Leopold LaCoste was Claude LaCoste’s biological father.


DNA Evidence for Claude’s Mother

Now that I knew who Claude’s father was, I turned to his mother. The Mary Crouchet who lived near Leopold in 1870 was born in September 1851 to a French father, Jean “John” Crouchet and a mother, Mary Anne Walker, of English and French descent. No Cajun! I can’t find her or Claude in the 1880 census. By 1900, she was a spinster living with her brother John’s family on Washington Street in New Iberia. Washington Street intersects Center Street, on which a newlywed Claude was living with his (first) wife’s family.

Mary Crouchet had no other children that I’ve discovered. To confirm that she was Claude’s mother, I needed to test descendants of her siblings. One such person was already in my mom’s match list. S.E. is the 2-great grandchild of Mary’s sister Octavia and shares 51 cM with my mom, 51 cM with her brother, and 20 cM with C.L. Those numbers fit well for a third cousin once removed. To confirm that the relationship was through Mary Crouchet, I sought out another person to test. Mary had six siblings who survived childhood. A couple of them married Cajuns, so I focused on the others. Several of their descendants either did not respond or were not comfortable with the idea of a DNA test.

Finally, I reached P.P., the granddaughter of Mary’s sister Bertha. She is a charming 91-year-old who readily agreed to do the DNA test and who invited my family to visit the next time we’re in the area. She shares glorious amounts of DNA with us: 196 cM (10 segments) with Mom, 103 cM (6 segs) with Uncle S., and 44 cM (3 segs) with C.L.! Best of all, she has very little Cajun ancestry, and S.E. has none at all that I can find. The only possible explanation for that much shared DNA in segments that large is that P.P. is the second cousin once removed to my mom through the Crouchet family.



The McGuire chart below summarizes the DNA results that proved who Claude’s parents were. Interestingly, I was able to solve this case without using the precise segment data available at GEDmatch or the other major DNA testing companies. J.W. was happy to chat but wasn’t that into the whole genealogy thing. A.A. and S.E. did not seem comfortable with the idea of transferring their raw data elsewhere. And by the time P.P.’s results came in, the segment data weren’t necessary.

This McGuire chart shows the DNA test results that proved who Claude LaCoste’s parents were. Claude’s direct ancestors and descendants are shown in bold. Names in red text have taken the AncestryDNA test. To read the chart, follow the line down and across from any person who has tested to see the relationship and how much DNA they share with another person. For example, S.E. is 2C2R (2nd cousin twice removed) to P.P, and they share 39 cM across 3 DNA segments.


I still have some unanswered questions about Claude LaCoste. One: where was he raised, and by whom? I’ve pored through the 1880 census for New Iberia and Lafayette and can’t find him or his mother. Two: did he have contact with his father’s family? Perhaps the record of his first marriage record that listed him as “fils leg.” meant that he had been formallly acknowledged by his father rather than that he’d been born within a marriage. Three: did my grandmother know? She was extremely intelligent and not one for polite fictions, and yet she insisted throughout her life that her father was from France. On the other hand, she was very young when he died, so everything she knew about him she must have learned from other people. No one who remembers my great grandmother LaPerle (Claude’s second wife) believes that she would have lied about Claude’s origins—she was too honest—and she must have known. New Iberia is a small town. But everyone agrees that LaPerle might not have corrected a story her young daughter invented on her own, because she would have viewed that as gossiping. I wonder how Mawmaw reconciled her belief that her father was French with the information on his death certificate.

In the end, I’m thrilled to have found Claude’s parents, and I’m content to let him hold on to a few mysteries.

17 thoughts on “Claude Duval LaCoste (1871–1926)”

  1. This was a fascinating read! Although I do not have any family from Louisiana, I do love genealogical mysteries, and am fascinated by the measures people take to uncover the truth. Thank you for posting this intriguing story. You might consider writing a book, your writing is that good.

  2. Really enjoyed your entry. Fascinating and well written. The variation in the amount of shared DNA between the the 2C1R (44 cM – 196 cM) really shows how random DNA inheritance can be.

  3. In the 1882 baptism, perhaps the lazy “y” in Couyet is actually a lazy “g”, so Couget, written after mis-hearing a spoken Couchet, which would sound very similar.

  4. Who was the Albert Elmer, informant on Claude’s 1926 death certificate, and how old was he, compared to Claude’s age at death of 55? This to try to gauge how close to the event of Claude’s birth he was, and how likely he was to be in possession of reliable knowledge pertaining to Claude’s birth?

  5. Thank you for all your hard detective work on this new relative in our line. I’m not sure I understand it all but will re-read. The last living great grandson of Leopold died a few years ago. My mother and I went to visit him. Now information must come via electronic devices.

  6. My mother’s family was French Canadian. I enjoyed your article and want to reread it a few times more. One ancestry match I had had nine lines connecting back, five to the husband who was my 7th cousin and four to the wife who was my 6 cousin 1x removed.

    However my 5th great grandfather on my father’s side is unknown. However like you I have a large number of DNA matches that I am curious about. I think rereading your article a few times may help me puzzle this out.
    Thank you for posting this.

  7. Since you cannot find your Claude’s birth, have you ever thought that your grandmother might have been right, and he was born in France? Did you perhaps look for the passenger list for the woman you consider to be his mother? Possibly look for exit of the US to France and then years later come back? Just an idea.

    1. I spent years trying to track down his immigration records from France. Turns out he wasn’t from France at all. I was able to prove with DNA who his parents were and that he was born outside of wedlock.

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