ST. PAUL — The founder of a Minnesota charity that has sent millions of books to schoolchildren in Africa hiked dozens of miles last weekend to mark his group’s 25th year.

Thomas Warth walked 48 miles from the University of Wisconsin-Stout, in Menomonie, Wis., to Hudson, Wis., last Friday and Saturday to raise awareness for Books for Africa.

Warth founded the nonprofit group in 1988, after he visited Uganda and saw a library in need of books. Since then, Books For Africa has shipped nearly 30 million books to 48 countries — making it the world’s largest supplier of donated textbooks and library books to Africa. This year, the group will give more than 3 million books.

The walk from Menomonie to Hudson wasn’t easy for the 77-year-old with a knee wrap. But he has hiked across Minnesota and Wisconsin before and has walked from the Canadian border to Iowa. He has also crossed the African nation of Gambia in support of the cause.

This year’s walk started at Wisconsin-Stout to recognize the thousands of books the university has donated over the years, Warth said. The walk also raised about $10,000 in pledges.

Warth said he is drawn to donating books because “they’re incorruptible.” He said they can’t be spent unwisely or used for anything besides education.

“The book will be read by someone even if it’s stolen,” he said.

During his weekend walk, Warth carried “A Transition to Advanced Mathematics” in his backpack. The college math textbook has a long way to go before it makes it to Africa, but he said he carried it as a symbolic gesture “for a book on the first part of its journey.”

Linda Amrein, 66, from Stillwater, was part of a group walking with Warth. She has been a supporter of the organization since she met Warth through her church.

“The books really do get to the children, get to the schools, get to the libraries,” she said.