Born Mary Stevenson Cassatt in Allegheny City, Pennsylvania, which is now part of Pittsburgh, she was the daughter of a well-do-to businessman. She was raised in an environment that greatly valued education, and her parents saw travel as a means to encourage learning. Before Mary was ten years old, she had visited many of the capitals of Europe, including London, Paris, and Berlin.
Cassatt lived in France for most of her professional career, like many of her contemporaries among American artists and literary figures. She began studying painting at the Pennsylvania Academy of the Fine Arts in Philadelphia, Pennsylvania (1861-1865), then in 1866 moved to Paris. By 1872, after she had studied in the major museums of Europe, her style began to mature, and in Paris, she became a student of Camille Pissarro.
Her first painting was accepted for the Salon in 1872. She was introduced to Edgar Degas in 1874, and he invited her to exhibit with him and other impressionists. She first exhibited in an impressionist show in 1879. From then until 1886 she was an active member of the impressionist circle, remaing close friends with Degas and Berthe Morisot.
She was influenced by Japanese prints in the late 1880s, and her interest is reflected in many of her paintings after 1890 of her favorite theme, the mother and child portrayed in intimate relationship and domestic settings. France recognized her contribution to the arts and awarded her the Legion of Honor in 1904. Although she had been instrumental in advising the first American collectors of impressionist works, recognition came more slowly in the United States.
In 1911, she was diagnosed with diabetes, rheumatism, neuralgi and cataracts. Her illnesses did not slow her down, but after 1914, she stopped painting because of failing eyesight. Nonetheless, she took up the cause of women's suffrage, and in 1915, she showed 18 works in an exhibition supporting that movement.
She died at Château de Beaufresne, near Paris, and was buried in the family vault at Mesnil-Théribus, France.
Recent sales of her paintings have been for as much as US$2.8 million.