ale Academy in Hartford; about 1870 or 1872, she engaged in additional study at the Philadelphia School of Design. Thaddeus attended Powers Institute, then went on to Amherst College. (He died March 14, 1865 -- perhaps of tuberculosis or consumption -- before graduating.) 
Almost a half-century later, Mary also reminisced about the "intellectual atmosphere" of the town during her youth, describing it as one that "somehow tended to make ambitious young people feel that the thing to do was to know, to read the best books, keep up . . . with the highest thought of the times." She spoke of "young folks . . . attend[ing] lectures by Emerson, Starr King, . . . Beecher, and other noted speakers" including Thackeray, and of "Dr. and Mrs. John F. Moors [her future in-laws] . . . showing pictures brought from Europe" and hosting Shakespeare readings.  All of these experiences helped enhance her education.
After matriculating from the Female Academy, Mary spent several years teaching in Greenfield and, briefly, in Wilmington, Delaware, before accepting employment at Franklin Savings Institution in either 1861 or 1864.  Biographical accounts note that she was the first woman employed by a Massachusetts bank -- and that she left the position after eight years, when the bank refused to pay her wages equal to those of her male counterparts.
It was during her time at the bank that Mary began publishing articles in local newspapers under the pseudonym P. Thorne. Although several sources state that Wells Smith's first published article was "Trials of a Tall Young Lady" in an 1858 issue of the Springfield Republican, "Trials" actually appeared on October 10, 1863. There is also some question whether "Trials" is her first piece, for in an 1875 letter, Mary indicated her earliest publication appeared in 1862. (She also explained her choice of pseudonym as "a wholly original inspiration, adopted in a spirit of reaction against the sickly sentimentalism then characterizing the nom-de-plumes of lady writers.") 
Several more short pieces for the Republican, mostly humorous, followed in late 1863 and early 1864, during which time she may also have been writing for the Unitarian periodical Christian Register. In addition to writing and working at the bank, Mary was active in local affairs, especially during the Civil War, when the town endeavored to make the soldiers of the 52nd Regiment stationed nearby comfortable and, after their departure, to provide them with additional aid via the local Sanitary Commission.  Ultimately, the combination of war work and Thaddeus's death may have limited her writing, for no publications have been located for 1865 or 1866.
For a brief period, Mary may have concentrated on writing for religious markets. Her next identified publication did not appear until 1867 -- an eight-page tract, published by the American Unitarian Society. Titled How To Be Happy: A Lay Sermon, it remained in print for over forty years (and, as recently as 2008, was used as the basis for a Universalist service).  She also may have begun writing for children during these years, for she had at least two short stories and a minor piece published in a juvenile periodical, the Sunday-School Gazette, in 1868.
By 1869, Mary had progressed from writing for local newspapers and Sunday-School periodicals to national magazines. Like her Republican pieces, these were primarily social commentary mixed with humor, not children's stories. "Pleasures of Poverty" appeared in Lippincott's in October 1869; a short story about farm life, "The Consequences," in Harper's in February 1870 (and was promptly excerpted in the Ohio Farmer), and one of her more telling pieces, "The Coming Woman," in Lippincott's in May 1870.
"The Coming Woman" -- somewhat ironic reflections on girls and women of the future -- suggests Mary's awareness of societal limitations on young women. In it, she speaks of a future with active, carefully educated girls, girls
who will be made to feel that something is expected of [them] too -- that [they] are to have a living interest in the world 