What effects did the underground railroad have on slaves and slave owners?
As to the slave owners, the underground railroad meant loss and expense. If their slaves successfully escaped via the underground railroad, the work on their farms and or plantations must either be divided up further among the remaining slaves or they had to purchase more slaves. If the work was divided up, it was less efficient because people doing more work makes them tired and slower at their tasks. If they had to buy new slaves, it was costly and would reduce profits from their plantations.
