The internet has brought some answers - and of course more questions - in my search for my great-great-grandmother, Mary Maume. Born in Ireland in the 1820s, she emigrated to New York in 1850, giving birth to her son, John Thomas, on the crossing. She left her son in an orphanage or other care for a few years so she could work; her employment was as housekeeper to George Turner, said to have been in the real estate business. She and Turner's gardener, George Frederick Helbert (from Hesse Darmstadt) fell in love and moved to Missouri together, taking Mary's son. They married in St. Louis on 7 Sep 1854 and settled on a farm in Gasconade county, south of Mount Sterling, where they raised a family. They stayed until George's death in 1890; he is buried on the property, with a tall and elaborate headstone. At some time after that Mary went to live with her daughter Annie at 130 Channing in St. Louis; she died shortly before 10 Feb 1900, the date a burial permit was issued. The farm in Gasconade has gone to seed and the house has burned.
When Mary's son John was around 18, she told him that Helbert was not his birth father; that his father was a John Murphy who had died on the crossing. In the 1870 census, the Helbert household shows Mary, George, their children, and twenty-year-old John Murphy. However, I've now heard from an Irish cousin who knows where Mary was from: Gortacurrig, Kildorrery, county Cork, where Maumes still live on the farm. The family believes Mary's child was born out of wedlock, and the biological father was not a Murphy at all. I doubt we can ever know, but it's certainly possible that the story of a deceased husband was invented to ease her difficult way over here.
In censuses John is shown as being born in June 1850. He was raised as John Helbert and he passed that surname along to his wife and children. There are no records I can find of a Mary Maume arriving in New York, but there are plenty of Mary Murphys, including one in 1850 with an infant. Since women could not vote, their citizenship was no issue; there is no naturalization record for Mary; no adoption record for John: Helbert became his legal father upon marrying Mary.
Although Gasconade county, Missouri, had many German immigrants in the mid-1800s, John married into an English family, Branson, from neighboring Osage, maintaining connections neither to an Irish community nor a German one. John raised his family mostly in Shannon county. They tried moving to Texas (Hill county, 1885) and to Oklahoma, but didn't stay long in either place. Mary Maume was Catholic, and it seems John may have been raised in that faith, but became Protestant (sometimes reported as Presbyterian, sometimes Baptist) when he married Hannah.
Mary had a brother William who also emigrated with his wife. He took part in the Civil War, fighting on the Union side in the Seventh Missouri Infantry, known as the "Irish Seventh", later merged with the 30th into the Missouri Irish Brigade or Battalion. I have requested his service record (having found no indication of any pension file) and will post whatever I learn.
Family tradition has it that John established and was first postmaster of the office at Wells Ford (named for Johnny Wells's family), between Eminence, Shannon Co and Salem, Dent county, Missouri. This does not seem borne out by the records, as a check of USPO personnel does not show his name, but he may have run a grocery that handled mail, similar to the store his wife Hannah had run at Grovedale. We know a few of John's activities: he operated a threshing machine; he raised and sold hogs; he bought Clydesdales and a gramophone, and put on little shows at fairs. He loved books, and was well-read. We don't know how much contact there was within the family after he was grown; he named his son after his half-brother, Charles Edward Helbert/Hilbert, who died in his early twenties; but my family only knew of one of his half-sisters, Annie, who came to live in St. Louis.
Online cousins are filling out more and more of the picture, as Patrick Fennessy in Ireland has identified Mary, her parents Thomas Maume and Elizabeth Gallagher, and her siblings John, Elizabeth, Catherine, Garret, Johannah, and William, along with their birthplace. In Missouri, cousin Mary Brown has supplied information on another of John's half-sisters, Mary, the only child of Helbert's with known descendants. I welcome hearing from Maume cousins anywhere.