From 2019 EJI Calendar
1851: Thomas Sims, who escaped slavery in Savannah, Georgia, is captured in Boston, and after a trial is ordered to return to enslavement.
From EJI Timeline
Thomas Sims Captured in Boston After Fleeing Enslavement

Boston flyer warning colored people not to talk with policemen.
In early 1851, Thomas Sims, an enslaved black man living in Savannah, Georgia, successfully escaped bondage and fled to Boston, Massachusetts — where slavery had been abolished. Only a few weeks later, on April 3, 1851, Sims was arrested by a United States Marshal and members of the local police force and taken to the federal courthouse to initiate proceedings to re-enslave him and return him to the South. Fearing riots or an escape attempt, authorities surrounded the courthouse with chains and a heavy police force.
In 1850, the U.S. Congress passed the Fugitive Slave Act, which sought to force Northern officials to apprehend black people fleeing enslavement as “runaway slaves” and ensure their return to enslavement in the South. Any official who would “hinder or prevent” the arrest of a runaway slave or “harbor or conceal” a fugitive slave faced a fine of $1000 or six months imprisonment. Captured fugitives – as well as the many free black people who were erroneously captured under the law as runaway slaves – had no right to a trial by jury and could not defend themselves in court.
The morning after Thomas Sims was captured, attorneys for his purported owner — a white man named James Potter — appeared to formally request his return. After a short proceeding in which several individuals testified that Thomas Sims had escaped from Potter’s possession, the Commissioner issued an order remanding Sims back to Georgia. Attempts to appeal to the Massachusetts Supreme Court and the United States District Court in Boston were unsuccessful; on April 12th, Sims was taken back to Savannah, where he promptly received 39 lashes as punishment for seeking freedom. The marshals who escorted Sims to Georgia received praise and a public dinner for their service.
After the Emancipation Proclamation and in the midst of the Civil War, Thomas Sims again escaped from slavery in 1863, this time fleeing Vicksburg, Mississippi, to return to Boston. In 1865, the Confederacy was defeated and the United States ratified the Thirteenth Amendment abolishing chattel slavery.