Due to a series of unfortunate events, it took decades for the Bell family to obtain their freedom.

Bell was an organizer and fundraiser for what was called "the single largest known escape attempt by enslaved Americans", by Vincent DeFort, a Washington, D.C., resident of the National Park Service.

[1] Having been thwarted many times by the court system and their slaveholder's behavior, the Bells were prevented from attaining their freedom.

Bell helped plan the use of a schooner, the Pearl, to transport his family north from Washington, D.C., in 1848.

Two days after their flight, the schooner was overtaken and Bell family members were taken back to the District of Columbia and held in a slave pen for sale.

[3][8] On September 14, 1835, Robert Armistead signed a deed of manumission to free Mary upon his death, but stipulated that her children should not be freed until they were 30 to 40 years of age.

[6] The deed of manumission was processed by a clerk of Washington County, Maryland and Mary Bell was given her freedom papers on September 21, 1835.

[6][8] Susan, however, contested her husband's manumission deed, stating that he was of unsound mind and coerced into signing.

[5] When Bell's slaveholder heard that Mary was freed and her children were to be freed by term slavery, he or she made arrangements with a slave trader who seized Bell, took him to Seventh Avenue, and placed in a slave pen to wait to be sold.

[3][8] The arrangements were made through abolitionists to buy Bell, and have him reimburse the purchase price in payments over time.

[8] Based on Susan Armistead's account of Bell's family in 1839—Andrew, Mary Ellen, and Caroline—the oldest children, were hired out.

[1][8][11][12] They planned on using a schooner, the Pearl, to transport the Bell family north from Washington, D.C., to Frenchtown, New Jersey.

[10] The plan became more harrowing when the decision was made to transport more individuals and families, resulting in a total of 77 fugitive slaves.

[1][9][10] Mary was among the group of 50 adults and children that were transported via railroad train from Washington, D.C., to Baltimore to be sold on April 21, 1848.

Daniel had tried to stop the train, telling the slave dealer that Mary was a free woman and that he had her freedom papers.