The first Thanksgiving was held either in Plymouth Plantation in 1621 or in St. Augustine, Florida in 1565. Obviously, everyone there was deceased by the time the first president was elected in 1789. The tradition of setting aside a day and a meal to thank God for his bounty continued in America, with no specific date until 1863, when Abraham Lincoln issued the first Presidential decree setting the date for Thanksgiving and proclaiming it a national holiday. Hence, the answer is either "none" or Abraham Lincoln, depending on how one defines "the first Thanksgiving."
President Thomas Jefferson
As President of the United States, George Washington proclaimed the first nationwide thanksgiving celebration in the US.
President Abraham Lincoln was the first to proclaim Thanksgiving a national holiday in 1863.
Thomas Jefferson is the president who scoffed at the idea of a national Thanksgiving day.
In the middle of the US Civil War, President Abraham Lincoln, prompted by a series of editorials written by Sarah Hale, proclaimed a national Thanksgiving Day, to be celebrated on the final Thursday in November 1863. It has been celebrated anually since. However President George Washington was the first President to issue a Proclamation that declared a National Day of Thanksgiving on October 3, 1789.
Sarah Polk is credited with having the first one at the White house.
The first president to observe a formal Thanksgiving dinner in the White House was Rutherford Hayes. Abraham Lincoln actually celebrated Thanksgiving, but the event was much smaller.
Technically Washington did however it did not become a federal holiday with a set date until Lincoln.
Thanksgiving was first proclaimed as a national holiday Abraham Lincoln, in 1863 during the US Civil War. This was set by law in 1941. (see related question)
NOPE, Canadian Thanksgiving was first though.
Abraham Lincoln
One turkey .