Rebecca had written for her own amusement since childhood and now had more time to concentrate on this part of her life, but she never intended in making a career of writing. In 1861 she was invited by an editor friend at the newspaper "Memphis Daily Appeal" to contribute a story. The main characters of this story were "little" Prudy Parlin, her sister Susy, and her cousins Grace and Horace Clifford. At the end of the story, she signed a version of her middle name,"Sophie", then she stopped a moment to select a surname. Finally she signed "May" because she thought, "I may write again and I may not." The story of Little Prudy was well received, and soon she was regularly contributing to Sara Jane Lippincott's "Little Pilgram", a Philadelphia children's magazine, as well as the magazine "Merry's Museum". Next her stories were noticed by the editor of the Boston "Congregationalist" newspaper. This editor invited Sophie May to send him "all she had to say about Little Prudy", and soon her stories were appearing in that publication as well. Sophie May never intended, at least not at that time, to have her stories put into book form, but the Congregationalist's editor offered some of them to a company which published Sunday School books. He received them back with a note that Prudy was "a cute chick, but not pious enough" for their uses.

Lee and Shepard Publishers of Boston finally bought the rights to these stories in 1863 for $50.00 on the recommendation of William T. Adams, who wrote the "Oliver Optic" children's books. Sophie May’s first series of six books were collected and published from 1863 – 1865 as the "Little Prudy" series. These books were an immediate success, and Sophie May started working on her next series in which the main character was Prudy's little sister "Dotty Dimple".

The Dotty Dimple series was published from 1867 – 1869. A letter Sophie May wrote in September 1867 to the publishers of her first series, Lee and Shepard, indicates that other publishing companies had taken notice of the new writer. In the letter Sophie writes, "I told them (Ashmead and Evans) I preferred my old publishers tho' we had made no definite bargains concerning future books....But, I have no wish to go from my old publishers to new ones unless I have reasons to think I can do decidedly better....But it does not seem to me a change would do me any good. I like you, and I like your enterprising manner of doing business. I think you have had very much to do with Prudy's success in the world." Starting with this series, Sophie May received a 10% royalty from all sales.

Frequent ill health seemed to limit the amount of writing Sophie May could get done each year. In 1869, Lee and Shepard wrote to her asking for another children's series, even though sources seem to indicate that Sophie was more interested in branching out into juvenile books for older girls. In Sophie's reply letter, she wrote, "But I really don't know what to undertake next. I have not an idea in my head beyond a delicious sense of relief that I have got that everlasting Parlin family tucked away." A year later, she was final convinced to write another children's series, telling her publisher, "Small children as a rule like repetition, otherwise I should not harbor the idea of more Parlins for a moment." The "Little Prudy’s Flyaway" series was published from 1870 – 1873. She also wrote the "Flaxie Frizzle" series (1876 – 1884), which introduced a completely new set of characters, and the "Little Prudy’s Children" series (1894 – 1901), about a grown up Prudy and her family. During her writing career, she did get to write a series of books for older girls, the "Quinnebasset" series. She also wrote several novel for adults, but they were not successful.

Sophie May’s childrens stories were very popular, with the "Little Prudy" series being published at least 20 times by at least six different publishing companies. In 1871, the "American Literary Gazette" recorded sales of her books had reached 300,000 copies. Her style of writing about realistic, mischievous characters was unusual in a time when most children’s literature was full of stiff instructions for living a ‘wholesome’ life. In the January, 1866 issue of the "North American Review", Thomas Wentworth Higginson wrote an article on the "Children's Books of the Year" for 1865. The Little Prudy series was listed as number 3 on a list of 22 books. In the article, the writer has a glowing review of the writing style of this new, unknown author.

(From the article) "None of the books thus far named [in the 1866 article], however attractive, can be said to have the touch of genius in them. Genius comes in with 'Little Prudy'. Compared with her, all other book-children are cold creations of literature only; she alone is the real thing. All the quaintness of childhood, its originality, its tenderness, and its teasing,--its infinite, unconscious drollery, the serious earnestness of its fun, the fun of its seriousness, the natural religion of its plays, and the delicious oddity of its prayers,--all these waited for dear little Prudy to embody them. Sam Weller is not more piquant; Hans Anderson's nut-crackers and knitting-needles are not more thoroughly charged with life. There are six little green volumes in the series, and of course other dramatis personae must figure; but one eagerly watches for every reappearance of Prudy, as one watches, at the play, for Owens or Warren to re-enter upon the stage. Who is our benefactress in the authorship of these books, the world knows not. 'Sophie May' must doubtless be a fancy name, by reason of the spelling, and we have only to be grateful that the author did not inflict on us the customary alliteration in her pseudonyme [sic]. The rare gift of delineating childhood is hers; and may the line of 'Little Prudy' go out to the end of the earth."

It was reported in 1892 that "before the advent of Prudy and her friends, children's books were wearisome, dull and priggish to an extent that the younger generations of today can scarcely realize." Sophie May was once called "the Dickens of the nursery" for her aim at writing books for children as young as six years old. She knew children would enjoy reading about the humor of everyday life. In fact, most of the events in her books were based on tales told to her by the older people of Norridgewock. A lot of her own village life worked its way into her stories. The characters in her stories seem to be based on her own nephews and nieces, because the Parlin and Clifford families in her stories have the same number of sons and daughters as certain Clarke families.

Sophie May's younger sister Sarah also became a contributor to magazines and a writer of children's books, although she was never as successful as her sister. She wrote under the pseudonym "Penn Shirley", and produced three 3 volume series; the "Little Miss Weezy" series, the "Silver Gate" series, and the "Boy Donald" series. She also produced one single volume book.

Sophie May's small hometown of Norridgewock, Maine is also the birthplace of Unitarian, clergyman and author, Minot J. Savage, and "Mary Densel" who also wrote children's literature. Later in life Sophie May's love for Norridgewock led her to present a building to be used as the town library. She traveled much, and spent her winters in Baltimore, Florida, as well as California. She died in Norridgewock on August 16, 1906, at the age of 73, and is buried in the Old Oak Cemetery there.