Final answer:
Maria Stewart's first accomplishment as a female abolitionist leader was giving a speech to a mixed audience, which broke barriers and challenged societal norms.
Step-by-step explanation:
In the 1830s and 1840s, Maria W. Stewart, an African American writer and activist, became the first American-born woman to give a speech to a mixed audience. Her speech marked an important accomplishment for female abolitionist leaders as it broke barriers and challenged societal norms. Stewart's achievement paved the way for other women to become active in the abolition movement and advocate for equal rights.