Anna Sewell (1820-1878) came from a literary background. Her mother Mary (nee Wright) (1797-1884) was a prolific author of children's books and Quaker religious tracts. Although her works are largely forgotten today, Mary was a popular children's writer during the middle Victorian period. As a young woman, Anna editted, proofread and critiqued her mother's texts, and undoubtedly picked up much of the writer's craft from her. Mary reciprocated this service for Anna while she was writing Black Beauty, and may in fact have collaborated on some portions of the book, although this is speculation.
At the age of fourteen, Anna fell on rain-slick pavement and injured her legs. Orthopedics being what they were at the time, the injury proved crippling, and she never recovered the full use of her legs. The Sewells were a country family, and well to do, so that Anna spent much of her youth and adulthood travelling about in a pony cart doing the charitable work that was expected of a Quaker lady.
Her love for horses is generally held to have sprung from her constant association with her ponies during this period. It's tempting to speculate on her as a sort of proto-furry, given her isolation from her peer group, and her closeness to her ponies. There's little beyond speculation to support this, however, as Sewell's surviving writings give little insight into her state of mind. She is known to have been in the habit of talking to her ponies, and at least one friend was of the opinion that Anna felt that the ponies had a basic understanding of her words, as well as a simple moral nature.
As she aged, her health declined, and throughout her middle years she was a frequent visitor to the various spas and healing springs of Europe. This threw her into the company of some of the middle Victorian period's leading lights of philosophy, arts and literature. This undoubtedly broadened her perceptions, and shaped her views on the role of animals and the poor in society; kindness to which was already one of the tenets of Anna's Quaker faith.
By 1866 she had become too frail to remain abroad, and retired to her mother's home near Norwich. It was here in 1871 that she began to write her novel. It was written over the next six years in fits and starts, with frequent interruptions necessitated by her ill health. In November of 1877 she sold her book to a publisher, seeing it published in time for Christmas. Although today 'Black Beauty' is widely read by children, in its original publication is was intended as a social tract for people who worked with horses, and Sewell was outspoken in her hope that it would lead to better treatment for them.
Anna Sewell died in March of 1878, having lived long enough to see her novel reprinted, as it proved more popular than the publisher had at first estimated. Over the course of the next few years, Black Beauty became one of the defining cultural icons of the late Victorian age, fully the equal of the modern 'Harry Potter' phenomenon.