Although we in New England have been celebrating Thanksgiving since 1621, not every in the country did. In fact, I remember when I was in Virginia, I heard that in 1607 Jamestown celebrated a Thanksgiving. And in Florida, the Spanish had Masses of Thanksgiving in the sixteenth century!
But the national holiday wasn't proclaimed a holiday until Abraham Lincoln made the proclamation. And he did so, because of Sarah Josepha Hale. She had been writing letters to presidents, since Zachary Taylor, suggesting the proclamation. You know Sara Josepha Hala, she wrote the nursery rhyme, Mary had a Little Lamb.