According to these articles, Lincoln established Thanksgiving as a national holiday on the last Thursday in November in 1863. Congress changed it from the last Thursday to the 4th Thursday in 1941.
http://www.smithsonianmag.com/history/what-was-on-the-menu-at-the-first-thanksgiving-511554/?page=1
http://en.wikipedia.org/wiki/Thanksgiving
From the Smithsonian:
"By the 1850s, most states and territories were celebrating Thanksgiving. Sarah Josepha Hale, editor of the popular women’s magazine Godey’s Lady’s Book, a trendsetter for running a household, was a leading voice in establishing Thanksgiving as an annual event. Beginning in 1827, Hale petitioned 13 presidents, the last of whom was Abraham Lincoln. She pitched her idea as a way to unite the country in the midst of the Civil War, and, in 1863, he made Thanksgiving a national holiday."
From Epicurious:
"There were undoubtedly native birds and game as well as the Wampanoag gift of five deer. Fish and shellfish were also likely on the groaning board.
The table was loaded with native fruits like plums, melons, grapes, and cranberries, plus local vegetables such as leeks, wild onions, beans, Jerusalem artichokes, and squash. (English crops such as turnips, cabbage, parsnips, onions, carrots, parsley, sage, rosemary, and thyme might have also been on hand.)
There is no concrete way to know if they had any roast turkey that day, but we do know there were plenty of wild turkeys in the region, 'and both the native Wampanoag Indians and English colonists ate them,' writes Curtin in Giving Thanks: Thanksgiving Recipes and History from the Pilgrims to Pumpkin Pie."
