The Thanksgiving story most of us hear is about friendship and unity. And that’s what Sarah Josepha Hale had on her mind when she sat down to write a letter to President Lincoln in 1863, deep into the Civil War. Hale had already spent years campaigning for a national day of thanksgiving, using her platform as editor of one the country’s most widely-read magazines and writing elected officials to argue that Americans urgently needed a national story. But she’d gotten nowhere – until now.Five days after reading her letter, Lincoln declared Thanksgiving a national holiday. At the time, …