Alpha Delta Pi was founded on May 15, 1851, at Wesleyan Female College in Macon, Georgia, making it the first secret society in the world for college women. Wesleyan was the first charted college for women in the world, and women who attended it could be as youngas fourteen or fifteen years old. It is thus fitting that six young women came together in this environment, and formed an organization which would still be thriving a hundred and fifty years later. Its founders were Eugenia Tucker Fitzgerald (the first president), Octavia Andrew Rush, Mary Evans Glass, Ella Pierce Turner, Elizabeth Williams Mitchell and Sophronia Woodruff Dews. By July 1, 1851 the membership had grown to thirteen.
The organization was originally called the Adelphean Society, named from the Greek word for "sister." The sisterhood went national in 1904, and in 1905 the name of the Sorority was changed to Alpha Delta Phi. By 1906 the Sorority had added four new national chapters, and held a national convention. In 1907 the first issue of the Adelphean, and the Sorority joined the National Panhellenic Conference in 1909. In 1913 the organization was again renamed, this time to Alpha Delta Pi Sorority, this change was done in order to avoid confusion with the Alpha Delta Phi Fraternity.
The Sorority reached its centennial in 1951, and celebrated with a Centennial Convention. The Memorial Headquarters were dedicated in 1955, and still remain in Atlanta. In 1979, the Sorority designated the Ronald McDonald House as its National Philanthropy, and in 1983 the Sorority established the Alpha Delta Pi Foundation, Inc. The 150th Anniversary Convention and celebration took place in Atlanta, GA, from June 28-July 2, 2001.