By Meredith Hamilton, Christian Science Monitor

As former first lady Barbara Bush celebrates her 90th birthday on Monday, she also marks the 25th year of her non-profit organization, a White House legacy that has continued to be an important part of her life.

Former first lady Barbara Bush is at the family summer home in Kennebunkport, Maine to celebrate her birthday with her loved ones, including her son, former Florida Gov. Jeb Bush, who is expected to run for president in 2016.

But she won’t just be blowing out candles. The Bush family matriarch is also backing a new mobile app that helps improve adult literacy skills. Bush plans on financially supporting a $7-million initiative by X Prize and Dollar General that will challenge developers to create a mobile app that helps illiterate adults learn to read.

Bush has been a long-time supporter of literacy programs. As First Lady she founded the Barbara Bush Foundation for Family Literacy, a non-profit dedicated to establishing “literacy as a value in every home,” according to the mission stated on the organization’s website.

But she didn’t stop after her husband left the White House. Just Sunday evening, she spoke at an event called “Celebration of Reading: 25 Years of Family Literacy,” a joint celebration of her birthday and of her foundation.

Many first ladies spend a bulk of their time in the White House working toward different philanthropic and policy-centered causes. Michelle Obama launched Let’s Move! in 2010, which strives to curb childhood obesity. Nancy Reagan pioneered the “Just Say No” to drugs movement and promoted the value of foster grandparents for displaced children and the elderly.

For Barbara Bush, the cause was and is literacy. She began her foundation in 1989, and 25 years later, it is still working toward the same goal.

Bush’s daughter-in-law, Laura Bush, has taken a similar approach, although she has focused on the importance of libraries in the development of children’s reading and learning skills.

A former librarian, Laura established the National Book Festival in Washington D.C. in partnership with the Library of Congress. The festival attracts more than 120,000 people annually.

She has continued her work through her own foundation, The Laura Bush Foundation for America’s Libraries. According to its website, the foundation “provides funds to our Nation’s neediest schools so that they can extend, update, and diversify the book and print collections in their libraries with the goal of encouraging students to develop a love of reading and learning.”

Laura may very well follow in her mother-in-law’s footsteps and continue her library cause for another 25 years, but, as Barbara told Time Magazine, “I try not to give my daughters-in-law advice, so they will come visit with my sons.”