At one time, slavery was commonplace and legal in both northern and southern states before the United States actually became an independent nation and afterwards. In Pennsylvania, there were blacks held in bondage well into the middle of the 1800s. Even while slavery was diminishing in Pennsylvania -- driven by Quakers and other Christian denominations - Cumberland County had more slaves than other county in the region.

In his new book, Slavery and the Underground Railroad in South Central Pennsylvania, historian Cooper Wingert writes about slavery in Cumberland, Franklin, Adams and York Counties. Unlike the large plantations in the south, most Pennsylvania slave owners had just a few slaves. But like the southern planters, Pennsylvania slave owners would advertise for return of escaped slaves -- something that Wingert chronicles in the book.

Under the law under which Pennsylania abolished slavery, slaves weren't freed until they were 28-years-old.

Wingert, who is 18 and will be a freshman at Dickinson College this fall has written 10 books since he was 12.

Cooper Wingert appears on Tuesday's Smart Talk.