Lew announced last summer that the Treasury was considering removing Hamilton from the $10 bill, to allow a woman to appear on the front of the currency for the first time since Martha Washington was taken off the $1 silver certificate.
The Treasury was moved in part by a viral campaign in early 2015 to put a woman's portrait on the new $20 bill in 2020, to mark the centennial of women's suffrage. The group "Women on $20s" received more than 600,000 online and in-person votes for a choice of 15 different women. Tubman received the most votes.
Treasury announced plans in June 2015 to honour a woman on the $10 bill, which was already slated for a redesign in 2020. The bills are regularly reworked to stop counterfeiting.
The campaign drew a backlash from supporters of Hamilton, who, as an aide to George Washington and the first secretary of the treasury, helped erect the US economic and banking system. Hamilton has gained notoriety in recent years due to the success of Lin-Manuel Miranda's Broadway play.
The debate sparked a grass-roots movement to remove Jackson, a slave owner whose divisive presidency included removing several Native American tribes from their lands in the South, from the $20 bill. Some point out that Jackson also opposed paper currency in favour of gold and silver.