11 Aug 1798 - Birth of his biological father John Clemens at Lynchburg, Campbell County, Virginia, USA 

18 Jun 1803 - Birth of his biological mother Jane Lampton at Columbia, Adair County, Kentucky, USA 

6 May 1823 - Marriage of parents at Columbia, Adair County, Kentucky, USA 

30 Nov 1835 - Birth at Florida, Monroe County, Missouri, USA 

27 Nov 1845 - (9 years) Birth of his wife Olivia Langdon at Elmira, Chemung County, New York, USA 

24 Mar 1847 - (11 years) Death of his biological father John Clemens at Hannibal, Marion County, Missouri, USA 

Mar 1847 - (11 years) Burial of his biological father John Clemens at Mount Olivet Cemetery, Hannibal, Marion County, Missouri, USA 

27 Oct 1890 - (54 years) Death of his biological mother Jane Lampton at Keokuk, Lee County, Iowa, USA 

30 Oct 1890 - (54 years) Burial of his biological mother Jane Lampton at Mount Olivet Cemetery, Hannibal, Marion County, Missouri, USA 

5 Jun 1904 - (68 years) Death of his wife Olivia Langdon at Florence, Città Metropolitana di Firenze, Toscana, Italy 

Jun 1904 - (68 years) Burial of his wife Olivia Langdon at Woodlawn Cemetery, Elmira, Chemung County, New York, USA 

21 Apr 1910 - (74 years) Death at Redding, Fairfield County, Connecticut, USA 

Apr 1910 - (74 years) Burial at Woodlawn Cemetery, Elmira, Chemung County, New York, USA