The establishment of the Middlesex County Antislavery Society followed close upon the founding of the New England Antislavery Society (1832) and the American Antislavery Society (1833). The county society—established by constitution as the "Middlesex Anti-Slavery Association, auxiliary to the New England Anti-Slavery Society"—held its initial organizational meeting on October 1, 1834 in Groton and its first quarterly meeting on January 27, 1835 in Concord. Its stated objectives were "to increase a knowledge of the nature and circumstances of Slavery—to ascertain its history—trace its influence on individuals and communities, and examine the different schemes for its abolition by inviting correspondence—by encouraging lectures, and discussions both written and verbal at its meetings, and by promoting the publication and distribution of such original and selected matter as may be considered worthy."
The membership of the society—which included both men and women—represented towns all around Middlesex County. A number of Concord people joined, among them Mary Merrick Brooks (who served on the nominating committee and as secretary of the organization), carriage maker William Whiting (a Main Street neighbor of Mrs. Brooks and president of the society), Dr. Josiah Bartlett, Helen and Sophia Thoreau (sisters of Henry David Thoreau), Monument Street farmer Minot Pratt; and minister John Wilder. Meetings were held in rotation in various Middlesex locations, Concord included.
In 1838 and 1839, antislavery organizations in New England were thrown into turmoil by disagreement over aspects of abolitionist leader William Lloyd Garrison's radical stance, particularly his promotion of women's active, voting involvement at meetings. Conservative clergymen and others who found it difficult to accept an equal role for men and women broke from Garrison's New England Antislavery Society to form their own organization (the Massachusetts Abolition Society). The Garrisonians were subsequently referred to as the "old orgs," the dissenters as the "new orgs."
Conflict over the role of women rocked the Middlesex County Antislavery Society in 1839. The issue of whether women should vote on resolutions flared up at a meeting on July 23, 1839, in Acton. The records show that those who supported women's participation in the business of the society prevailed over those opposed to it (54 to 46), prompting a group of the defeated party to walk out of the meeting "for the purpose of forming a new society."