BETHEL — Janet Hayward Burnham has written children’s books, romance novels and history books over her lifetime, but her most recent undertaking is perhaps her most ambitious.

“20th Century Book: Bethel, Vermont,” which was published by the Bethel Historical Society last month, spans the years of 1900 to 2000 and is around 300 pages long.

“It could have been double that amount,” Burnham said during an interview at Bethel Town Hall, where the historical society has its museum. “This is probably the most extensive project I’ve done.”

Burnham, 86, who has also written for magazines, started working on the book about five years ago. It had been on her mind for a few years. The last retelling of Bethel’s history was published more than a century ago: In 1895, Fred G. Cox published a book called “Bethel Illustrated,” which the historical society reprinted in 2001.

While other books about certain parts of Bethel town history — including one about town hall architect George Gurnsey and another about the Italian immigrants who moved to Bethel to work in the quarries, which Burnham co-authored — have been published since then, there hasn’t been another expansive retelling until now.

“Because of belonging to the historical society, I thought there were things that needed to be written down and kept,” Burnham said. She wanted to create an accessible account of Bethel’s 20th century that would be of interest to people in town — as well as those who have moved away or those with interest in Upper Valley history — that would combine photos and writing. “It was an enormous amount of work, but over a period of time.”

It took Burnham hours of work to do a single page. Some of the more difficult parts to research were confirming the names of Bethel residents who served in the country’s wars and tracking the history of various businesses in town. There’s a section about the 14 schools that used to exist in town and another about the town’s churches. Around 70 families in Bethel also submitted pages of their family history, which Burnham edited before including in the book.

The biggest challenge for Burnham was choosing what to include.

“When you talk about 100 years, there’s an awful lot going on,” Burnham said.

Burnham became involved in the historical society when she moved to Bethel around 1984 with her late husband, George. She quickly immersed herself in town history.

“She’s really kept up well with our history over the years,” Joanne Marshall, president of the Bethel Historical Society, said during an interview at town hall alongside Burnham. That made her the perfect person to take on the new book. “A lot of this was not new to her.”

Burnham let her research drive her writing process: Sometimes, she started with text and found a photo to go along with what she’d written. Other times she’d come across an engaging photo, which led her to do more research. Burnham typed up each page on her computer and other historical society members proofread them.

All proceeds from the book, which costs $32, will benefit the Bethel Historical Society. Burnham is pleased with the finished book and the way it came together.

“There’s no particular fa vorite part,” Burnham said. “It’s all (my ) favorite.”

Copies of “20th Century Book: Bethel, Vermont” can be ordered via facebook.com/BethelHistSoc.

Liz Sauchelli can be reached at esauchelli@vnews.com or 603-727-3221.