Among the nation's oldest athletic clubs, the Boston Athletic Association was established on March 15, 1887 under its first president, Robert F. Clark, and with the support of leading sports enthusiasts, entrepreneurs and politicians of the day. According to Article II of the B.A.A.'s 1890 Yearbook Constitution, their objective was to encourage all manly sports and promote physical culture.

"There is no more important part of our mission than that. It's to help people be as fit and as healthy as they want to be." - Tom Grilk, B.A.A. Chief Executive Officer

In 1888, the B.A.A. completed its magnificent clubhouse in Boston's Back Bay on the corner of Exeter Street and Blagden Street, on the present-day site of the new Boston Public Library. In addition to such facilities as a gymnasium, bowling alley, billiard hall, Turkish baths and tennis courts, the Association also owned a shooting range and a country club. Active sports of the day included boxing, fencing, water polo, and athletics.

The club held its first organized track and field competition in 1890. The Association chose a mythical unicorn as its symbol, which remains on the Boston Marathon medals to this day.

Ten years after it was established, the B.A.A. held the 24.5-mile B.A.A. Road Race to conclude the B.A.A. Games, a springtime athletic competition. The Boston Marathon, as the race would later become known, was held on April 19, 1897 with a starting field of 15 runners. Ten participants finished the inaugural run, which began in Ashland, Mass., and the race to Boston has been held in every subsequent year. In addition to its indisputable position as the world’s oldest annual marathon, “Boston” is widely regarded as one of the world’s most prestigious road races. The Boston Marathon is held on Patriots’ Day (third Monday in April). The centennial Boston Marathon was on April 15, 1996 and drew one of the world’s largest field of finishers (35,868).

In 1936, the clubhouse closed due to financial hardship. The Boston Athletic Association is now headquartered at 185 Dartmouth Street in Boston's Back Bay. In 1986, John Hancock assumed the sponsorship of the Boston Marathon and saw the race into the next millennium.

The B.A.A. continues to rely on the generous support of John Hancock and other sponsors and contributors not only with its signature event, the Boston Marathon, but also in its year-round community programming.