AHEAD OF HER TIME: Sarah Josepha Hale, who pushed to make Thanksgiving a national holiday, was an accomplished writer and editor. In this illustration from Mike Allegra’s book “Sarah Gives Thanks,” she works with the printer of Lady’s Book, the most widely read magazine in the country.

Mike Allegra is sitting cross-legged on the floor in the children’s section of Barnes & Noble in Princeton MarketFair. A group of youngsters and a few parents are wandering in after hearing an announcement over the public address system that a reading is about to begin.

“Who’s looking forward to Thanksgiving?”, Mr. Allegra asks enthusiastically, searching the faces assembling around him. The response is lukewarm — at first.

It only takes a few moments for Mr. Allegra, who is the editor of The Lawrenceville School’s alumni magazine The Lawrentian, to warm up his young audience. By the time he starts telling the story of the woman whose persistence convinced President Abraham Lincoln to declare Thanksgiving a national holiday, the kids are rapt.

That woman is trailblazing 19th century writer and advocate Sarah Josepha Hale. She is the focus of Sarah Gives Thanks, the children’s book Mr. Allegra collaborated on with illustrator David Gardner. Ms. Hale was, in Mr. Allegra’s words, “the Oprah of her time.”

“What Sarah did in her lifetime is not what other women were doing at that time,” he said last week. “She became the editor, or editress, as she liked to say, of the most widely read magazine in the United States. She also promoted education for women, founded and supported charities, wrote and edited books, and raised five children as a single mother after her husband died young. She was incredible.”

Mr. Allegra discovered Ms. Hale’s story when the publisher Albert Whitman & Company asked him to write a children’s book with a Thanksgiving theme. After doing some research at The Library Company in Philadelphia, he realized he had a great story on his hands.

“Here was someone who was really important, but whose story was not widely known,” he said. “This is the woman we can thank for making Thanksgiving a national holiday, and not many people know that. And that’s only part of the story.”

As Mr. Allegra tells it, Ms. Hale was always interested in writing. But as a woman in early 19th century New Hampshire, she was expected to be a wife and mother and not much more. Her husband, a lawyer, was the only one to encourage her. When he died young, leaving her with five small children, she was devastated. She wore black for the rest of her life.

The book begins with the family around the Thanksgiving table, just after Mr. Hale’s funeral. While she gives thanks for the food on their table, she knows she has to think of a way to support the family. After unsuccessfully selling hats for a while, she turns to writing. Soon, Boston magazines are featuring her articles and poems. She publishes books, too, and becomes a household name.

“Each fall, Sarah wrote about Thanksgiving in her magazine,” the book reads. “She explained how it promoted family, friendship, gratitude, and religion. She even offered a delicious recipe for pumpkin pie.”

In early to mid-19th century America, Thanksgiving celebrations were relegated mostly to the New England states. But Ms. Hale’s work made the holiday more popular. In 1894, she began an annual tradition of making her case to the president. Zachary Taylor, Millard Fillmore, Franklin Pierce, and James Buchanan ignored her requests. But Abraham Lincoln finally gave in after receiving Ms. Hale’s letter. On October 3, 1863, he issued a proclamation declaring a National Day of Thanksgiving the last Thursday of November.

Among the reviews for the books is one from the School Library Journal. “…this well-researched, engaging read-aloud offers youngsters a glimpse into the lives of women and families in 19th-century America as well as to the history of how Thanksgiving became a national holiday …. Generous, full-spread watercolor illustrations add humor and colorful details.”

“So we have Sarah to thank for Thanksgiving,” Mr. Allegra said. “She was a remarkable woman and it was fascinating to learn about her.”