The 43rd treasurer of the United States is keenly aware, for example, that on the third floor of the Treasury Department, there is not a single woman among the portraits of the country's ex-treasury secretaries. And in the male-dominated world of finance, female senior executives are few and far between.

So after being sworn in as treasurer in 2009, she became fixated on a goal: putting a woman on U.S. currency.

Her quiet campaign burst into public view last month when Treasury Secretary Jack Lew announced to national fanfare that a woman of historical significance will be featured on the next $10 note.

"When I got to the point where I actually mentioned (my children) Brooke and Joey's name in my remarks, I got choked up," Rios, who turned 50 on Friday, said in a recent interview in Washington. "That's hardly ever happened before in my entire life but it hit me -- it hit me then that this was going to happen."

While the new design won't be unveiled until 2020, the announcement is sparking a spirited national debate about which woman should grace the $10 bill. There's also some grumbling about putting a woman on the $10 note rather than the $20, even though the Treasury Department has explained that the decision was largely driven by security considerations.

Hillary Clinton, who is trying to make history of her own by becoming the country's first female president, has shared her two cents.

"I don't know why they picked the $10 bill," she told CNN's Brianna Keilar earlier this month. "I think a woman should have her own bill and it may be more appropriate to look at the $20 than the $10."

Rios shrugged off the debate over why a woman is being placed on the $10 note rather than the $20 and why founding father Alexander Hamilton is being booted rather than former President Andrew Jackson.

"I just haven't heard that outside of D.C.," Rios said. "For the most part, I think people are excited that this is happening. This is historical."

Modest upbringing

As treasurer, Rios oversees the U.S. Mint, the Bureau of Engraving and Printing, and Fort Knox. Her signature is featured on all circulating denominations of U.S. paper currency, and she works out of a spacious corner office at the Treasury Department overlooking the White House lawn.

But Rios didn't have an elite upbringing.

She was one of nine children born to Mexican parents who immigrated to the country in 1958. Her father left shortly after Rios' youngest sibling was born, leaving her mother to raise her children largely on her own.

"She's a survivor. She never hesitated in what she was teaching us," Rios said of her mother. "It was the three F's in my family: family, food and faith. And she reinforced that every step of the way."

With her mother stressing that education was the ticket to a better life, Rios was a voracious reader as a child and poured herself into her studies. She graduated from Harvard University in 1987 and in the private sector, she worked her way up to a managing director position at a real estate investment firm in San Francisco.

In 2009, President Barack Obama nominated Rios for the treasurer job.

Valerie Jarrett, a senior adviser to the President and head of the White House Council on Women and Girls, said Rios' humble upbringing shapes the treasurer's approach to her work.

"She comes into this extraordinary, important role never forgetting where she came from," Jarrett said. "She spends a lot of her time thinking about how to encourage women to go into the fields such as finance where they are under-represented and she's a great example of this success story."

The unveiling of the new $10 bill design in 2020 will coincide with the 100th anniversary of women getting the right to vote. In an unusual move, the Treasury Department is taking suggestions from the public, encouraging people to submit their ideas through the Treasury website as well as social media using the hashtag #TheNew10.

Leading contenders

A poll conducted by "Women on 20s," a popular campaign to get a woman on the $20 bill, showed that the leading contenders were Harriet Tubman, Eleanor Roosevelt and Rosa Parks.

Rios and other senior administration officials have been careful to avoid singling out any personal favorites. But asked to name a political role model, Rios was quick to name Shirley Chisholm, the first African-American woman elected to Congress.

Photos: Women on currency Photos: Women on currency On Wednesday, Treasury Secretary Jack Lew announced that a woman would appear on the U.S. $10 bill in 2020 . There have been just a handful of women on U.S. currency in history. Susan B. Anthony, the 19th-century feminist leader, appeared on the dollar coin from 1979 to 1981 and again in 1999. Hide Caption 1 of 17 Photos: Women on currency The dollar coin has suffered in popularity in recent decades. The Treasury tried a different tack in 2000 with the Sacagawea dollar, a gold-colored coin featuring the Lewis and Clark guide. Despite heavy marketing, it never really caught on, though it's still minted for collectors. Hide Caption 2 of 17 Photos: Women on currency Helen Keller, the deaf-blind author and activist whose inspiring story was told in the play and film "The Miracle Worker," appears on the reverse of the Alabama quarter that was part of the 50 State series. It includes writing in Braille. Hide Caption 3 of 17 Photos: Women on currency Martha Washington, President Washington's wife, was the first woman to appear on U.S. currency and to this day is the only one on a banknote. She appeared on $1 silver certificates in 1886, 1891 and 1896, the latter with her husband. Hide Caption 4 of 17 Photos: Women on currency Though the U.S. has tended to stick with politicians and statesmen, other countries have been more willing to feature artists, writers and other kinds of civic leaders on their currencies. In Mexico, the 500-peso note features painter Frida Kahlo on the reverse and her husband, Diego Rivera, on the obverse. Hide Caption 5 of 17 Photos: Women on currency Queen Elizabeth II is prominently featured on the currencies of a number of Commonwealth countries, including the UK, Canada, Australia, New Zealand and Fiji. Hide Caption 6 of 17 Photos: Women on currency Argentina celebrated "Evita," former first lady Eva Peron, by putting her on its currency. She's shown here on a 2-peso bill in honor of the 50th anniversary of her death and has appeared on the country's 100-peso note since 2012. Hide Caption 7 of 17 Photos: Women on currency Legendary actress Greta Garbo will start appearing on Sweden's 100-krona note in October. Hide Caption 8 of 17 Photos: Women on currency Author Jane Austen, known for such works as "Pride and Prejudice" and "Emma," is scheduled to come to the British 10-pound note in 2017. Hide Caption 9 of 17 Photos: Women on currency Scientist Marie Curie appeared on the Polish 20,000-zloty banknote in the '80s and '90s. She also appeared on the French 500-franc note with her husband, Pierre. Hide Caption 10 of 17 Photos: Women on currency Golda Meir, who served as Israeli Prime Minister from 1969 to 1974, appeared on the country's 10,000-shekel note, changed to a 10-shekel note after a devaluation in 1985. Hide Caption 11 of 17 Photos: Women on currency Bertha von Suttner, the first woman to be awarded the Nobel Peace Prize, is depicted on Austria's 2-euro coin. Hide Caption 12 of 17 Photos: Women on currency Opera star Dame Nellie Melba appears on the Australian 100-dollar note. Hide Caption 13 of 17 Photos: Women on currency Sigrid Undset, who won the Nobel Prize in Literature in 1928, is featured on Norway's 500-krone note. Hide Caption 14 of 17 Photos: Women on currency Corazon Aquino, who served as president of the Phillippines from 1986 to 1992, appears on the country's 500-peso note with her husband, Benigno Aquino. Hide Caption 15 of 17 Photos: Women on currency Before the country switched to the euro, Germany had pianist and composer Clara Schumann on its 100-Deutschmark banknotes. Hide Caption 16 of 17 Photos: Women on currency When Italy's currency was the lire, the country featured educator Maria Montessori on the 1,000-lire note. Hide Caption 17 of 17

Rios has fought to elevate women in Washington in other ways. She pushed for the first Women in Finance Symposium in 2010, which has since become an annual tradition.

And soon after being confirmed treasurer, she lobbied then-Treasury Secretary Tim Geithner to redecorate the walls of the long, marble-floor hallway outside her office. Today, the "Gallery of Women in Treasury" lines those walls — an exhibit that shows snapshots of women's contributions to the U.S. Treasury Department over the centuries.

One of those portraits is from 1878, of a woman working on a coin press.

Asked how that woman might react to the decision in 2015 to put a woman on the $10 bill, Rios answered: " 'What took us so long?' "