While Little Free Libraries numbered zero in 2009, the popular take-one-leave-one book boxes total more than 36,000 worldwide this year, including 18 officially mapped within a mile of the University of St. Thomas.

Wisconsin native Todd Bol set up the first Little Free Library in Hudson as a tribute to his mother, and since that single library opened, the movement has spread so much that the program aims to count 100,000 boxes worldwide by the end of 2017.

“They really touch every corner of the globe,” said Margret Aldrich, author of “The Little Free Library Book.” According to the nonprofit’s website, all 50 U.S. states and more than 70 countries sport the little libraries.

The concept is simple: Stewards, as they are called, can either build or buy a pre-made library, register it with the nonprofit for about $45 and add its coordinates to the site’s world map if they choose. Then, they fill the box with books and watch the neighborhood do the rest.

“I thought it was going to be me filling it up all the time, or my neighbor, but it’s not,” said Little Free Library steward Gretchen Cudak, who splits upkeep duties of her Summit Avenue library with her next-door neighbor. “It’s really give and take.”

Passersby can take or leave any books they wish, and Cudak says she has rarely had trouble with inappropriate book donations or vandalism in her four years of maintaining the library.

“Every once in awhile the glass gets broken, that kind of thing,” Cudak said. She and her neighbor have replaced the window in the box’s little door with Plexiglass, which can better withstand Minnesota weather and the occasional vandal.

Still, Aldrich said that neighbors so appreciate Little Free Libraries that even if one does get damaged, it is quickly repaired.

“If something bad happens to a Little Free Library, the community kind of rallies around it and helps the steward re-build or re-stock it or re-paint,” Aldrich said.

Aldrich thinks that sense of community and informal sharing is what has made the Little Free Library movement so popular.

“It’s like opening a present,” Aldric said. “When you see one on a block, it feels like a friendlier place.”

St. Paul resident Deb Draeger understands the gift-like aspect of Little Free Libraries. She said she checks her nearby libraries regularly just to see if any new books have arrived.

“(It’s) every time I walk by,” Draeger said.

New books arrive often, Cudak says — sometimes in the arms of passersby, other times in the trunks of drivers who stop when they see her library.

Nationally, Little Free Library has facilitated the exchange of more than 9.3 million books by 2016, according to its website. It’s something Cudak sees echoed in her own little box of books.

“(The library) always seems to have something in it,” Cudak said.

Elena Neuzil can be reached at neuz3833@stthomas.edu.