How was Boston different from other cities regarding escaped slaves?

The Massachusetts Supreme Court decisions in Walker v. Jennison and Commonwealth v. Jennison established the basis for ending slavery in Massachusetts on constitutional grounds, but no law or amendment to the state constitution was passed. Instead slavery gradually ended "voluntarily" in the state over the next decade

Explanation:

Fugitive slave. Fugitive slave, any individual who escaped from slavery in the period before and including the American Civil War. In general they fled to Canada or to free states in the North, though Florida (for a time under Spanish control) was also a place of refuge.