Considered "the most prominent of the [American] women etchers in the late 19th century," Mary Nimmo Moran produced a large number of prints that were celebrated for their boldness and originality.

In 1847 the artist and her brother emigrated to the United States from their native Scotland with their widowed father, a weaver named Archibald Nimmo. The family settled in Crescentville, Pennsylvania, where their neighbors, English immigrants named Moran, introduced Mary to their son Thomas, a well-known artist. At 18 Mary began to study drawing and painting with Moran; two years later they were married and moved to Philadelphia. The couple had two daughters and a son, and in 1872 they relocated to Newark, New Jersey.

While Thomas achieved success with his oil renditions of the western United States, Mary concentrated on painting the landscape near their home. Although she sometimes traveled with her husband-to the West, Florida, and Europe-during the early years of their marriage Mary was too busy taking care of the children, managing the household, and assisting her husband to do much painting. She came into her own as an artist in 1879, when Thomas introduced her to the technique of etching. Working in this medium Mary achieved success: she was elected to the Society of Painter-Etchers of New York; she became the only woman among the 65 original Fellows of London's Royal Society of Painter-Etchers; her prints won awards and were collected by such prominent individuals as the English critic John Ruskin. Rather than being overshadowed by her spouse, on many occasions when both husband and wife exhibited etchings in the same show, it was Mary's work that was singled out for praise.

In 1884 the Morans built a new home on Long Island, the surrounding area of which became the subject of many of Mary's most successful etchings. She died in 1899 of typhoid fever, after nursing their daughter Ruth through the same disease.