By the 1820s, the growing whaling industry attracted workers from all different backgrounds, including free and escaped African Americans, Pequot and Wampanoag natives, Cape Verdeans, Pacific Islanders, and Europeans. The job opportunities and diversity within the city fostered a civil rights movement and opportunities for people of all backgrounds.
In 1830, New Bedford's population totaled 7,592 residents; by 1834, the number of black seamen in the city nearly quadrupled. By 1837, the population and economy had grown so much that New Bedford officially became a city. Its 16,000 residents included 1,047 African Americans, 400 of whom were fugitive slaves.
Black men owned property, paid taxes, and could vote. Black families lived among white ones in some neighborhoods, and black children attended schools with white children, although they were seated separately.
In 1833, African Americans created the New Bedford Union Society, an antislavery group. The following year local black and white abolitionists created the New Bedford Anti Slavery Society.
When Congress approved the Fugitive Slave Act in 1850, which required citizens to return runaway slaves to their masters, New Bedford Quakers Sarah Arnold and Elizabeth Rodman gathered 1,729 signatures to petition for its repeal.
By 1853, New Bedford housed 1,008 African American inhabitants; 700 of them were escaped slaves. By 1855, the city had 20,389 residents.