Harriet Tubman is in; President Andrew Jackson is out.

U.S. Treasury Secretary Jacob Lew's decision to replace Jackson on the front of the $20 bill with abolitionist and Underground Railroad conductor Tubman has been widely praised. It honors women's role in American history and, indirectly, disparages slave-owner Jackson, who moves to the back of the $20 bill. But there is another irony to Jackson's traditional place on the $20 bill: He was an ardent critic of paper money.

To illuminate this oft-forgotten part of the story, we put some questions to historian Jessica Lepler of the University of New Hampshire and author of "The Many Panics of 1837: People, Politics, and the Creation of a Transatlantic Financial Crisis." Here are her edited and condensed answers: