Country music legend Dolly Parton has been called a lot of things over the course of her five-decade career: singer, songwriter, actress and cartoon character (her words). But none of those titles has meant more to the 72-year-old than the one she celebrated at the Library of Congress: “book lady.”

Parton is the founder of Imagination Library, a nonprofit that started out donating books in Sevier County, Tenn., and grew into a million-book-a-month operation. Families who sign up receive a book per month from birth to kindergarten. The singer donated her organization’s 100 millionth book to the nation’s library on Tuesday.

“I never thought about being ‘the book lady,’ ” she joked during the event. “The painted lady, yes, the overexaggerated lady. That goes to show you can’t judge a book by its cover.”

One person who got a particular kick out of Parton’s part-time gig as a librarian? Her dad.

“He took so much pride that little kids called me the book lady,” Parton said. Robert Lee Parton Sr., who died in 2000, never attended school and couldn’t read or write, Parton explained. She didn’t grow up with any books in her childhood Tennessee home, save for the Bible. The Imagination Library, started in 1995, was a way for the singer to honor her father.

“I wanted to do something special for him,” she said. “In the Bible, it talks about honoring your father and mother.”

After a brief chat with Librarian of Congress Carla Hayden, Parton, dressed in a cream-colored sweater suit, carefully made her way off the stage to sit closer to a group of preschoolers from the area. She read to them from her children’s book “Coat of Many Colors” and even sang some of the words, her perfect voice echoing through the great hall.

“Of all the things I’ve done in my life — and it’s been a lot because I’ve been around — this is the most precious,” she said. “Maybe we’ll be back for a billion.”