Crandall’s steadfast commitment to the education of these young women was immediately tested by withering opposition from Connecticut residents who refused to tolerate a school for young women of color. Despite this hateful reaction, she continued to operate the school. Finally, the state of Connecticut passed the “Black Law,” which barred the teaching of “any colored people...not inhabitants” of Connecticut without a town’s permission. Crandall was arrested, spent a night in jail, and faced three trials as her case became a cause célèbre throughout the country. While awaiting trial, she continued to operate her school despite threats of violence and denials of service on the part of the townspeople of Canterbury and even despite the poisoning of the school’s drinking water well. Her continued defiance drew sharp criticism not only from local citizens but also from politicians, religious leaders and others from across the state. State Senator Andrew T. Judson, who spearheaded the passage of the “Black Law,” even went so far as to state, “...we are not merely opposed to the establishment of that school in Canterbury; we mean there shall not be such a school set up anywhere in our state. The colored people can never rise from their menial condition in our country.”
Her first trial resulted in no verdict, but in the second she was convicted. A third trial, an appeal before Connecticut’s Supreme Court, overturned the conviction and dismissed the case altogether. Arguments from her trials were later used in Brown v. Board of Education, the Supreme Court's landmark school desegregation decision of 1954.
Connecticut repealed the “Black Law” in 1838, but Crandall had already left the state. Despite the dismissal of the case, townspeople in Canterbury continued to vandalize Crandall’s school. Following a mob assault two months after the case dismissal, she was forced to close the school. She and her husband, the Reverend Calvin Phillio, moved to Illinois. She did not, however, abandon her commitment to education. There she opened a school in her home and continued to work to further the rights of women.
Crandall continued her interest in the reform movement throughout the rest of her life. At the urging of Mark Twain and others, the Connecticut Legislature did penance for its earlier prosecution of Crandall by granting her a small pension in 1886. Prudence Crandall died in Elk Falls, Kan., in 1890, leaving behind a legacy of equal education and the fight for reform. The Prudence Crandall Museum in Canterbury, Conn., celebrates this legacy and is a site on both the Connecticut Women’s Heritage Trail and the Connecticut Freedom Trail.