LEWISTON – The Twin Cities latest joint effort will make a difference in the wallets of more than 6,000 residents.

It might actually make them thinner.

Officials from both cities Wednesday unveiled a new joint library card good at both Lewiston and Auburn libraries. It will replace individual cards in both cities.

“Libraries across the state are interested to see how this works,” said Rosemary Waltos, director of the Auburn library. “I think a few might be interested in doing the same thing, if it works.”

Auburn residents can pick up their cards free of charge when their current card expires. Lewiston residents can replace their cards right away for a $1 fee.

The cities have granted library privileges to each other’s residents for the last 30 years, according to Rick Speer, director of the Lewiston library. He estimated some 6,000 Twin Cities residents carry both cards in their library.

“It’s a pretty even split, I’d guess about 3,000 in each city,” he said.

Waltos said the card has been in the works since last fall, and members of each library’s board of directors agreed to the new card in December. They’ve been working since then to make sure most of their policies and systems match.

Due dates for books will be the one remaining difference. Lewiston has a grace period, giving residents an additional two weeks to return the book once it is due. Auburn begins charging fines to residents as soon as a book is late.

“That will probably be the next discussion we have, adopting uniform due date rules for both libraries,” Waltos said.