This definitely sounds like the John Andrew Wanless I've been looking for -thank you!
Ancestry.com shows his birth as "about October 20,1835" in South Carolina.
Re his 2nd marriage - I have it from Ancestry.com as "before 1904." It was probably around 1889. Leonard was indeed born February 17,1904 and died in July, 1983 in Rolla, MO. My grandfather, Edward Arrivee Wanless was born April 1, 1890 and died July 13, 1976 in St. Louis, MO.Helen Arrivee was the oldest, born March 21, 1897, and died on August 26, 1975.
Do you have any more information regarding John Andrew's parents, Archibald and Margaret (Moorehead)?
It would appear that we share the same great-grandfather.