This is me, playing catch-up with my research logs, in an attempt to narrow the search for my great grandfather's birth date without the benefit of a birth certificate. If anyone sees anything I missed or any flaws in my analysis, please let me know.
Subject Name: Louis Phelisa Lanctot, b. ?? d. Oct 1922
Question to be researched: When was Louis born?
Date of Search: 11.6.11
Place Searched: ancestry.com (1900 U.S. Census, Charles Mix Co., SD, (Darlington Township), p. 8B, li. 54-60)
Results: "Lewis" is shown as being 12 years old, born in Sept 1887 in Nebraska. Son of "Jenophile" (b. Canada) and Elizabeth (b. Illinois). However, the census was taken on 21 Jun 1900, placing Lewis’ birth date between 22 Jun 1888 and 20 Jun 1889. This may be a mathematical error on the part of the enumerator, or incorrect information given.
Place Searched: Ancestry.com (1910 U.S. Census, Cedar Co., NE, (St. Helena/Precinct 2), p. 10B-11A, li.96-2.)
Results: "Lewis" Lanctot is found working as a laborer at the household of Walter Lawson. He is 22 years old, single, born in Nebraska, father from Canada, mother from Illinois. His occupation is listed as well driller. Census was taken on 13-14 May 1910, which translates to a birth date between 15 May 1888 and 12 May 1889.
Place Searched: ancestry.com (1920 U.S. Census, Natrona Co., WY, (Election District 8, Enumeration District: 84), p.2B, li. 75-59.)
Results: Louis T. Lanctot, age 32, listed with wife Alice. He was born in Nebraska, father from Canada, mother from Illinois; occupation well driller. Census was taken on 17 Jan 1920, which translates to a birth date between 18 Jan 1888 and 16 Jan 1889.
Place Searched: ancestry.com ("World War I Draft Registration Cards, 1917-1918," digital image [database online], Ancestry.com, card for Louis Phelisa Lanctot, no. 75, Converse, Wyoming.)
Results: Louis Phelisa Lanctot of Yankton, SD, DOB: 17 Sept 1888 in Mead, Nebraska. Occupation: independent well driller. He is married with 2 children.
Place Searched: Edward John Lanctot, Casper, Natrona, Wyoming, USA birth certificate 2686 (30 July 1921).
Results: Louis Lanctot listed as age 33 at time of Ed’s birth, making his birth date between 31 Jul 1888 and 29 Jul 1889.
Place Searched: Yankton Cemetery, Yankton, South Dakota, headstone
Results: Shows Louis P. Lanctot’s birth year as 1887.
Place Searched: L.P. Lanctot and Alice M. Schnieder, (15 July 1913), South Dakota Marriages, 1905-1949 [database on-line]: ; South Dakota Department of Health, Pierre, South Dakota.
Results: Listed as age 25 at time of marriage (15 Jul 1913), making his birth date between 15 Jul 1888 and 14 Jul 1889.
Analysis: All the information I have to date provides a birth date for Louis between September 1887 and 29 Jul 1889. I do not put a lot of weight into the date given on the 1900 census, because there is clearly some error there (mathematical or otherwise). I also do not put a lot of weight into the information inscribed on the headstone, since I don’t know where that information came from, or who provided it. Therefore, for all the ages used to be correct, I am left with a birth date range between 31 Jul 1888 and 16 Jan 1889. I would tend to believe the date of birth on his WWI Draft Registration, except that it is considered secondary information (he would not remember the date of his birth), although that date does fall within the range of dates in my analysis.
Conclusion: Louis Lanctot was born between 31 Jul 1888 and 16 Jan 1889.