Dear Reinhard,
I have Gebhardt ancestors. There are a 28 Gebhardt Families in St. Louis, Missouri USA on the 1870 census. More if spelled Gebhart. Many state that they originate from Hessen. There are many more on the 1880 census in St. Louis, Missouri which index is viewable for free at Familysearch.
My 2GGM name was Mary/Marie Gebhardt. She was born circa 1850 and immigrated to the U.S. in 1856 per the U.S. 1910 Missouri Census. I believe she had a brother William born circa <1858?> in Missouri.
I thought perhaps I had located her family on the 1870 census':
Father - John Gebhardt (age 54) b. Hesse Darmstadt circa 1826
Mother - Marie Hautz (age 50) b. Prussia circa 1830
Chilren
- Mary (age 19) b. Missouri ?
- William (16) b. Missouri
- Lizzie (13)
- Louise (11)
- Amelia (9)
- Adam (6)
Located the John (Gebheart) family in 1880 minus Mary and William, with a few more chidren 
and mother in law Eliza. Hautz b. Circa 1806 Prussia.
I suspect my Mary Gebhardt married about 1872. So of course she would not be enumerated with the family. Did find a marriage record of a Marie Gebhardt and Gerhard MeyerPeter April 1872. A civil record. Located a copy on microfilm and unfortunately no mention of a Pastor or Church 
Or address :(.
I located Mary Gebhardt-Meyer on the 1880 Federal Census Missouri.
Her husband was Listed as Henry Meyer, however he was later known as August Meyer. Family tradition states that the surname was originally MeyerPeter. It states Mary Gebhardt was born in Prussia and on this census she is listed as age 31. I am certain this is my Mary as the children, August, Lizzie and Matilda in the household were relayed to me by a cousin.
Unsure of what my 2GGF first name really was..lol. Gerhard? August? or Henry?. Perhaps all three.
I also located William Gebhart, born in Missouri on the 1880 Federal Census, with wife Charlotte/Charlotta and mother-in-law Elizabeth MeyerPeter. (In 1910 this William also lived on the same street as my grandmother lived prior to her marriage in 1935, could possibly even be the same house.)
So I had assumed likely Mary and William Gebhardt married siblings and that John and Marie were her parents. Seemed to fit, though the age listed for William was questionable, then I discovered there are 2 William Gebhardt's on the 1880 census. The other William's age is correct to the family of John Gebhardt and Marie Hautz and not to my family. So back to Square one..lol.
I do believe that my Mary Gebhardt did have a brother named William though due to his inlaw being named Eliza. MeyerPetter/MeyerPeter and later residing on the same street as my Grandmother (would be his great Niece), in 1935. Seems to coincidental not to be related.
I assume she was Lutheran or Evangelical as her obituary states that she was buried in "Lutheran" Cemetery.
However, her daughter Emma Meyer/Meyers (My GGM) was married in the Catholic Church.
Anyway I am stuck on this family :). I suppose looking for a 6 year old named Mary Gebhardt on an unindexed passenger list be pretty tough to find.
But I hope the information about the many Gebhardt's in St. Louis, Missouri will assist someone.
Regards,
Barbara