Her mother, Mary Wright Sewell, was a success children's author, and Anna helped edit her books. After suffering an injury in her childhood Sewell depended on carriage horses as her main source of mobility. Her empathy for the horses spurred her to begin writing Black Beauty in 1871 with the hopes of changing the way horses were treated. Although Sewell died just 5 months after Black Beauty was published, in April 1878, the book became and remains a classic, selling over 50 million copies in 50 languages. The popularity of the book did have an effect on the treatment of horses, namely in the discontinued use of the 'bearing rein.'