Harrigan will succeed Uri Barnea, who was dismissed after 20 years in 2004.
Harrigan founded the Baltimore Chamber Orchestra in 1983 and led that group for two decades. She is currently music director of the Battle Creek (Michigan) Symphony and the Lafayette (Indiana) Symphony.
"We couldn't be more happy," said BSO board president Lynn Fox. "I think she's very good at motivating musicians. She has a high energy level, and she has the most experience with an orchestra among the finalists."
The other finalists were Dennis Simmons; Barbara Day Turner, music director of the San Jos_ Chamber Orchestra; Glen Cortese, music director of the Oregon Mozart Players; and Raffaele Ponti, music director of Italia Konzert Opera in Florence.