Rosie Rios: Real reason behind $10 bill change

There is one practical reason why the U.S. Treasury Department decided to move forward with adding a woman to the $10 bill, U.S. Treasurer Rosie Rios said Thursday.

"The primary purpose of a currency redesign is security. In 2013, we decided that the $10 note would be the next note for redesign," Rios said in a CNBC "Squawk on the Street" interview.

Nevertheless, Rios added that adding a woman to the $10 bill is a continuation of the Obama administration's efforts on gender equality. "For us, this is very symbolic … because the timing of this is such that it will be unveiled in 2020, which is also the 100th anniversary of the 19th amendment, granting women the right to vote."

The department announced Wednesday it would incorporate the image of a woman on the $10 bill.

Read MoreJack Lew: Here's the remedy for strong dollar pain

"With such a wide reach, America's currency makes a statement about who we are and what we stand for as a nation," U.S. Treasury Secretary Jack Lew said in a statement, adding that "this decision of putting a woman on the $10 bill reflects our aspirations for the future as much as a reflection of the past."

The year 2020 will also mark the first time in over 100 years that a woman was featured in a U.S. currency, Lew added. Martha Washington and Pocahontas were both featured on bills during the 1800s.

Rios also said the only concrete criteria needed for a woman being featured on the note is that she has since passed away. Still, she added that "What we're looking for is a woman who has contributed to the history of this country and that best represents the theme of democracy."

The department is also taking suggestions as to who should be on the note through the site thenew10.treasury.gov and by using the hashtag "#The New10" on social media.

—CNBC's Everett Rosenfeld contributed to this report.