There had been women's social associations earlier in the century, but most were church-sponsored or auxiliaries to men's organizations.  While women had played an important role in the numerous reform movements of the Antebellum Era, societal norms required that men provide the leadership.  In 1868, two women's groups were founded and run by women to give women an opportunity for self-improvement and community service.  In Boston, Julia Ward Howe organized the New England Women's Club, and Jane Cunningham Croly was the driving force behind the establishment of Sorosis in New York City.

Croly was a journalist with a national reputation.  In 1855, she joined the staff of the New York Tribune and soon became one of the first women in the United States to write a syndicated column (under the name Jenny June).  She and her husband briefly published a newspaper in Rockford, Illinois, and then returned in 1860 to New York, where they both worked for the New York World.  She also wrote and edited for other publications and her own books.  When her husband contracted Bright's Disease in 1879, she financially supported her family (including four children) through her work as a journalist, editor, and author.  After his death in 1889, she took a position as professor of journalism and literature at Rutgers University, becoming the first American woman to teach news writing.

Croly had long wanted to open opportunities for women and for women to play a greater role in molding American society.  The specific event sparking the creation of Sorosis occurred in April 1868 when the New York Press Club decided to bar women from its dinner honoring Charles Dickens on his American tour.  Although the Press Club agreed at the last minute to open their doors to women if enough expressed a desire to attend the Dickens's soiree, it was too little too late to satisfy Croly and her friends.  (Years later, the Press Club formally apologized to Sorosis.)

Joining Croly in founding Sorosis in April 1868 were other notable women of the period, including Kate Field, a journalist and author, Anne Botta, a writer for the New York Ledger and author of children's books, Ellen Louise Demorest, coeditor (with Croly) of a women's fashion magazine, sisters Alice and Phoebe Cary, both poets, Ella Dietz Clymer, a writer, and Celia Burleigh, soon to be an ordained minister.  The organizational meeting at Delmonico's restaurant in New York City was itself a challenge to socially acceptable behavior since it was not deemed proper for women to be seen in public places without a male escort.  

In order to become a member of Sorosis, women had to be invited, pass inspection, take a loyalty oath, and pay an initiation fee of five dollars.  Members were usually career women (often by necessity, not choice) and represented many professions, but were concentrated in fields most open to women, primarily journalism and literature.  Most of the women were middle-aged, white, and middle or upper-middle class, and many were involved in various reform efforts.

In founding Sorosis, Croly wanted to improve women's status both in the private and public spheres.  She acknowledged and honored women's special role in childbirth and child rearing, but wanted to make women more efficient homemakers so that they could devote more time to improving themselves and the culture around them.  Sorosis meetings offered a chance for women with similar ambitions to socialize, educate themselves, gain self-confidence, and make contacts for career advancement.  

Members and guest speakers gave presentations on a variety of topics, although the divisive issues of religion and women's suffrage (which Croly supported) were spurned.  Even though some members dissented from the policy, Sorosis refused to align itself with any other group or cause.  Committees existed for literature, art, drama, music, philanthropy, science, education, house and home, and business.  Concerning art, for example, discussions focused on how women were portrayed in art or on female artists.  The club sponsored scholarships for female art students, and members bought paintings and sculptures by female artists.  By the end of the century, numerous women's clubs across the country had been established on the Sorosis model, including associations of African-American women.