What years was the underground railroad active? and how many people were estimated to be free to because of the railroad?

Why do you have to ask such hard questions.

It developed as a reaction to the impact of european colonialism in africa on peoples of african descent. in the  mid-20th century, activists in africa adopted pan-africanism as a rallying cry for independence from colonial rule. some african pan-africanists sought to unite the continent as one independenthope it was useful