What woman author helped in making Thanksgiving a national Holiday?

The woman who played a key role in making Thanksgiving a national holiday was Sarah Josepha Hale.

She was a writer, editor, and poet who was a strong advocate for establishing Thanksgiving as a national holiday. Through her writing and lobbying efforts, she was able to influence President Abraham Lincoln to declare Thanksgiving a national holiday in 1863.

While she didn't single-handedly create the holiday, Hale's work was instrumental in its widespread adoption and recognition as a national celebration.