According to a website on female artists, "Little is known about Sarah Catherine Martin." Oh, I do like a challenge.
Sarah, you'll recall, was the lady who reputedly created the famous verses featuring Old Mother Hubbard and her dog. A dig around the web turned up a number of conflicting stories about how Sarah came to create the book which formed the basis for the Old Mother Hubbard we know today—the old lady who went everywhere to try and feed her dog. The early verses—perhaps as many as three—are thought to have already existed. Certainly Old Mother Hubbard did, as can be seen from the following advert, which appeared in The Times on 17 April 1799.
From this we can see that Old Mother Hubbard was already considered a "juvenile amusement" of the same type as "See Saw, Margery Daw", "Little Jenny Wren" and "Humpty Dumpty". The fact that these amusements were available at music shops makes me think these were song sheets rather than the chapbooks that began appearing in the early 19th century.
It does, however, establish that the notion of Old Mother Hubbard pre-existed before Sarah Catherine Martin conceived her version. It seems likely that Sarah took the existing version and expanded upon it, adding illustrations. The original version of the story was submitted to a London publisher, John Harris, and a single copy was produced for presentation. The presentation copy was dedicated to John Pollexden Bastard, Esq., M.P., "at whose suggestion and at whose house these notable sketches were designed." The dedication was dated June 1, 1805. A year later, John Harris contacted the author with the idea of printing the story as a chapbook. A print-run of 10,000 copies sold out quickly and new editions followed, as did a variety of editions from other publishers.
The dedication helps locate where Sarah Catherine Martin was in 1805: she was, it is suggested, the housekeeper to Bastard, the Squire of Yealmpton, Devon. See, for instance, the Pictures of England site which relates how "The Nursery rhyme "Old Mother Hubbard" was written and illustrated by Miss Sarah Catherine Martin in 1804, following her retirement as housekeeper of nearby Kitley House, the estate of Sir Henry Bastard." Sarah, it is said, moved into a thatched cottage nearby (now a restaurant). "Sarah continued to live out her retirement in Mother Hubbard's cottage."
The Bastard family had acquired Kitley when William Bastard (1667-1703) married the heiress Anne Pollexfen (d. 1723). By 1805, the estate was run by William's great-great-grandson, John Pollexfen Bastard (1756-1816), a politician and militia officer, who was M.P. for Devon from 1784 until his death.
John Pollexfen Bastard had married Sarah, the widow of Charles Wymondesold, in around 1780; following her death in 1808, he married Judith Anne Martin (c.1772-1848), the daughter of Sir Henry Martin, on 2 July 1809.
Judith Anne Martin was the sister of Sarah Catherine Martin. Their father, Sir Henry Martin (1733-1794), 1st bart, was the eldest son of Samuel Martin, esq., by his second wife, Sarah, daughter of Edward Wyke, lieut.-governor of Montserrat. Sir Henry married Eliza Anne, daughter of Haring Parker of Hillbrook, Co. Cork, the widow of Hayward Gillman, on 26 November 1761. Sir Henry's children included Eliza Anne Martin, Henry William Martin, Josiah Martin, Judith Anne Martin , Lydia Martin, Samuel Martin, Sarah Catherine Martin and (Admiral Sir) Thomas Byam Martin (1773-1854).
Sarah, born in 1768, is often described as the housekeeper of the Kitley estate of Sir Henry Bastard, although John Pollexfen Bastard had succeeded following his father William's death in 1782, who had succeeded on his father's death in 1733. Quite where Sir Henry Bastard fits in, I don't know.
Whether she was the housekeeper also seems a little uncertain... she was, after all, the daughter of the MP for Southampton; perhaps she required work following his death in 1794 (at which time she would have been in her late 20s), although the association with the Bastard household appears to date back even further, at least to around 1785 when, we are told (by the previously cited Pictures of England site), that Sir Henry Bastard was the Resident Commissioner of the Navy in Portsmouth.
He counted amongst his friends Prince William Henry, later to become King William IV. Prince William was struck by the 17-year-old Sarah Catherine Martin and "the Prince is known to have visited the estate and many legends abound in the area about Sarah and the Prince." One is that the Prince proposed marriage (see, for instance, here) but the marriage was not allowed because of her (Sarah's) lowly background. Again with the lowly background: her father, Sir Henry Martin, was comptroller of his Majesty's navy, and an MP, which can hardly be described as a lowly background. In this latter version, upon retiring to Old Mother Hubbard's cottage, Sarah writes the famous rhyme to express the frustration at never being able to marry the man she loved.
A third version of how the story came to be written can be found here, where we learn that Sarah's sister married Edmund Pollexfen Bastard (1758-1816), MP for Tomes, although this is in error—Edmund was married to Jane Pownoll in 1783 and remained married to her until his death. However, ignoring this for a second, "Edmund's second marriage was to Judith Ann Martin, sister of Sarah Catherine Martin. When Sarah wrote the Old Mother Hubbard nursery rhyme she was staying with Judith and wrote the rhyme for her nieces and nephews."
It was, in fact John Pollexfen Bastard who married Judith Anne Martin, in 1809. The couple had no children, as proven by the fact that Edmund succeeded him to the Kitley estate on his death. So Sarah was supposed to have written Old Mother Hubbard for non-existent nieces and nephews four years before her sister's marriage.
Sarah Catherine Martin remained unmarried and died in 1826, and was buried at the parish churchyard in Loughton, Essex. The Martin family had connections with Loughton through relatives, the Powells, who lived there. At least this is the information that can be gleaned from "Loughton: Worthies and Social Life", pp.117-18, A History of the County of Essex, Vol. 4 (1956) (online here).
At this point I'm willing to admit defeat. I can believe that Old Mother Hubbard was supposedly the housekeeper at Kitley and this has somehow become transferred to Sarah Catherine Martin who, it seems to me, is a very unlikely housekeeper. If it was she who drew the illustrations for Old Mother Hubbard and Her Dog in 1805, she seems an accomplished artist. The success of this and the book's sequel, A Continuation of the Comic Adventures of Old Mother Hubbard, published by John Harris in 1806 and which has been attributed to Sarah Catherine Martin, begs the question, why did she not write or illustrate anything further?
Only four points of her life are in even the smallest part estabished: her birth in 1768, a proposal of marriage by Prince William when she was 17, writing and illustrating Old Mother Hubbard in 1805 and her death in 1826, aged around 59. That leaves an awful lot of gaps to fill.