Nothing is left of the building — which bordered the railway tracks — except ash.
Including books, some 60,000 items are gone.
The library was next door to the Musi-Cafe, where dozens of patrons and employees died after the July 6 tragedy.
The archives were personal — more than two dozen families had donated various documents, items and heirlooms since the library opened in 1991.
Diane Roy, chairwoman of the library's board of directors, said the archives included letters penned by her uncle dating back to the Second World War.
Other items included some of the oldest photos in existence of Lac-Megantic as well as the negatives.
Also gone forever are a few hundred works of art — reproductions, originals and some that were being housed on loan.
"We lost everything, all of it's gone except for those books that are in the homes of people who'd borrowed them," Roy said in an interview.
"It represents a big, big loss."
Roy said the library housed one of the most extensive collections of documents about Canadian outlaw Donald Morrison, who was involved in a blaze in Lac-Megantic in 1888 that triggered a year-long manhunt and then a gun battle in the heart of the town.
The Library and National Archives of Quebec says the loss of the Lac-Megantic archives is huge.
''They were unique, original documents and we don't have copies of them in our possession," said spokeswoman Martine Rouette.
Rouette said the library is ready to provide its expertise to Lac-Megantic to help it rebuild.
"We are available to them,'' Rouette said. ''There is really a (sense of) solidarity among libraries."
The downtown location was never meant to be a permanent space for the library, but temporary digs somehow turned into 22 years.
It served about 3,000 people a month. A dozen computers in a lab room were in use all the time.
"We are still a region that is quite far-flung and not particularly wealthy," Roy said. "So people could come and it was always full because not everyone in town had the means to buy themselves a computer."
The library was supposed to move this year and share space with the local college in a larger space in town.
The provincial government had authorized a grant earlier this year. Renovations had begun just two weeks ago to the new space — an old factory — and the move was scheduled to be done before November.
Roy said she found out about the explosion from her 85-year-old mother, who lived about 50 metres from the epicentre of the explosion. Roy said when she heard about the blast, her thoughts immediately turned to the library.
''The chief librarian's office was practically on the tracks," Roy said.
Authors and publishing houses have begun donating signed first editions for the new library.
"It will take some time before everything is ready but in the meantime authors have been donating their books, signed, to restart the library with as many personalized items as possible," said Simon-Pier Labelle Hogue, one of the people behind the project.
"We've received a lot of support from authors, publishers, distributors. Some of them in Europe have decided to send their complete collections."
Meanwhile, Roy said calls have been pouring in with artists offering artwork to rebuild the collection. Townspeople have offered more heirlooms and pieces to begin replenishing the archives.
The harrowing photos and documents from the fire will be among the first items in the new facility.
"If not for the fact that we had another building under construction, I'd probably be crying instead of having some hope," Roy said.
"We're starting at zero but we've been there before."
On the web: https://www.facebook.com/DonDeLivresALaBibliothequeDeLacMegantic
- By Sidhartha Banerjee in Montreal.