Hello Philip, I have a copy of Maude Blanche Chaney's "GENEOLOGY OF THE HICKENLOOPER FAMILY" of February 18, 1929. This is specifically the ancestry and descendants of Thomas Hickenlooper who settled in Albia, Monroe, Iowa. I was given a copy by a descendant, but it may be available through the DAR or through the Iowa State Library.
It lists two Mary Hickenloopers who were first cousins: Mary Isiephene, the daughter of Simon, and Mary, the daughter of Theophilus. I think it is the latter that you want. From other sources I have her born in 1856 in Monroe County, Iowa and married to John Hayes.
This is what Maude Blanche Cheney has for Theophilus: "Theophilus was born May 2, 1829, in Armstrong County, Pennsylvania.He was married to Margaret Gray, June 29, 1854, in Monroe County and died April 20, 1887 at the age of 57 years, 11 months, and 18 days.His death seemed to have been caused from an injury and liver trouble.He lived on a farm about seven and one-half miles southeast of Albia.Children:Mary, Frank, Harry, Arthur, twin babies (unnamed), Ella and Thomas."
You might try the Monroe County, Iowa USGenWeb site. I haven't been there for some time, but I remember it as having lots of information.
I have a complete family group sheet on Thomas Hickenlooper and his wife Julia Ann Hawkins as well as the Hickenlooper ancestry straight back to Germany, which my great aunt Melva Hickenlooper obtained in the early 1960s. My cousin, Max Jensen, has since been to the ancestral village near Stuttgart.
The US Hickenlooper ancestry for Mary begins with Andreas Heckenleib/Heckenlaible and Anna Catharina ?? Andrew Hickenlooper, Jr. and Rachel Long Thomas Hickenlooper and Julia Ann Hawkins Theophilus Hickenlooper and Margaret Gray
If you are interested in Hickenlooper ancestors -- that is, if this is a direct line for you -- please contact me directly. I probably have most availableHickenlooper material. If you can fill out my information on Mary -- dates and places of birth, marriage, and death -- when you write me directly, that would be very kind.