A fellow researcher (S. Varonka) has provided me the following information on Casper/Caspar Miller, who is my wife's great-great-grandfather. If this is the right person, Emma's maiden name was Clark.
"1. Caspar Jacob Miller, born Abt. 1847 in Toby Twp., Clarion Co. Pa.; died in Sumber Twp, Trempealeau, Wi.. He was the son of 2. Jacob Miller and 3. Lydia M. Flick. He married (1) Emma W.."
I would be interested in tips on where to find
1) Marriage date (perhaps 22 April 1874) and place for Casper and Emma
2) Date of death and burial location for Casper
3) Date (1853?) and place of birth for Emma, and parents
4) Place and date of death and burial location for Emma
5) Confirmation that their children include Archie Columbus Miller, born 29 March 1878 somewhere in Wisonsin and died 30 July 1955 in Redfield, SD (as per his death certificate).
Siblings of Archie may have included Britton, Allan, Ruby, Manley, Dora, Deborah, Della, Delia and Dorothy.