By 1874 Cassatt had established herself in a studio in Paris. Three years later, her parents and her sister Lydia joined her in France. Her family frequently served as models for her work of the late 1870's and 1880's, which included many images of contemporary women at the theater and the opera, in gardens and parlors. Always single-minded and self-reliant, Cassatt now had the opportunity to concentrate on her art in a city where, as she later said, "women [did] not have to fight for recognition if they did serious work."
Cassatt had a painting accepted and praised at the Salon of 1872, and she exhibited her work at the Salons of the next few years. However, when one of her entries was refused by the Salon in 1875, and neither of her entries was accepted in 1877, she became disenchanted with the politics and traditional tastes of Paris's official art world. When the artist Edgar Degas invited her in 1877 to join the group of independent artists known as the Impressionists, she was delighted. She was already an admirer of Degas's art, and she soon became close friends with Degas; the two frequently worked side by side, encouraging and advising each other. She also socialized with other fellow artists in this circle. Camille Pissarro, for example, was an older member of the group who acted as a mentor to Cassatt. Berthe Morisot was another female artist who exhibited with the Impressionists; she was a close contemporary to Cassatt, and she shared Cassatt's concentration on domestic scenes.
Cassatt exhibited her work with the Impressionists in Paris from 1879 onwards, and in 1886 she was included in the first major exhibition of Impressionist art in the United States, held at the Durand-Ruel galleries in New York. She continued to specialize in scenes of women in domestic interiors, with an Impressionist emphasis on quickly captured moments of contemporary life, and she expanded her technique from oil painting and drawing to pastels and printmaking. Japanese art had been very popular in Paris since it was featured at the 1878 Exposition Universelle, and Cassatt (like many Impressionists) incorporated its visual devices into her own work. She also shared with the Impressionists a general conviction that academic art was outdated and a commitment to exploring fresh new means of depicting everyday modern life.
By the 1880's, Cassatt was particularly well known for her sensitive depictions of mothers and children. These works, like all her portrayals of women, may have achieved such popular success for a specific reason: they filled a societal need to idealize women's domestic roles at a time when many women were, in fact, beginning to take an interest in voting rights, dress reform, higher education, and social equality. Yet Cassatt's depictions of her fellow upper-middle-class and upper-class women were never simplistic; they contained layers of meaning behind the airy brushwork and fresh colors of her Impressionist technique. Cassatt herself never married or had children, choosing instead to dedicate her entire life to her artistic profession. She shared and admired progressive attitude of Bertha Honore Palmer, a businesswoman and philanthropist who invited Cassatt to paint a mural for the 1893 World's Columbian Exposition and who felt that "women should be someone and not something."
After 1900, Cassatt suffered from failing health and deteriorating eyesight. In 1904 Cassatt was recognized for her cultural contributions by the French government, which awarded her the order of Chevalier of the Legion d'honneur. She made her last visit to the United States in 1908. By this time she had suffered several personal losses; her beloved sister, Lydia, died after a long illness in 1882, and her brother Alexander, the president of the Pennsylvania Railroad, died in 1906.
By 1914, due to her increasing blindness, Cassatt was no longer able to work, although she continued to exhibit her art in exhibitions including the Suffrage Loan Exhibition of Old Masters and Works by Edgar Degas and Mary Cassatt at the Knoedler Galleries in New York in 1915. She lived primarily in Grasse during World War I before returning to her country home, a chateau located in Le Mesnil-Theribus, fifty miles northwest of Paris. Cassatt died on June 14, 1926.
Cassatt was active into the 1910's, and by her late years she was able to witness the emergence of modernism in Europe and the United States; however, her signature style remained consistent. The waning critical taste for Impressionism after her death in the 1920's meant that her influence on other artists was limited.
However, Cassatt's status in art history has been significant and influential in the later twentieth and twenty-first centuries. She is considered one of the most important American expatriate artists of the late 1800's. She has also been the focus of influential scholarship on female artists, and her work has been discussed by key feminist art historians. Cassatt's most public legacy may be her influence on American patrons who collected her work and the work of her European contemporaries and later bequeathed it to museums. One prominent example was Louisine Elder Havemeyer, a close friend whose extensive collection of Impressionist art is now a part of the Metropolitan Museum of Art in New York.