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John Adams declared Thanksgivings in 1798 and 1799, while James Madison declared the holiday twice in 1815.  After 1815, there were no further national Thanksgivings until the Civil War, although in 1817 New York State adopted Thanksgiving Day as an annual custom.
The southern states were generally unreceptive to a "Yankee" custom being pressed on them by the federal government.  The New England states continued to declare annual Thanksgivings usually in November, although not always on the same day; with most of the other states eventually having independent observations of the holiday. 
New Englanders, during their great westward migration, introduced their favorite holiday, with Thanksgiving first being adopted in the Northeast and Northwest Territory, and then by the middle and western states.  By mid-century, the southern states were celebrating their own Thanksgivings.
Thanksgiving became an important symbol of the new emphasis on home life.  The holiday focused on the home and hearth where it was hoped a revolution in manners would begin to restore the civilized virtues which had been lost in the new commercial and industrial society.  Newspapers and magazines helped popularize the holiday as a secular autumn celebration featuring feasting, family reunions and charity to the poor.
Sarah Josepha Hale, a New England author and editor of the influential Godey's Ladies Book, in 1827 began lobbying several presidents for the instatement of Thanksgiving as a national holiday.  Mrs. Hale was a leading figure in the domesticity movement and lobbied for a return to the morality and simplicity of days gone by.  Each November from 1846 until 1863, Mrs. Hale printed an editorial urging the federal government to establish Thanksgiving as a national holiday.  Eventually, the fruits of her hard labor came to pass in 1863.
President Abraham Lincoln declared the first of our modern series of annual Thanksgiving holidays for the last Thursday in November 1863.  He had previously declared national Thanksgivings for April 1862 and again for August 6, 1863, after the northern victory at Gettysburg. 

The date of Thanksgiving may have been set by President Lincoln to somewhat correlate with the anchoring of the Mayflower at Cape Cod, which occurred on November 21, 1620, by our modern Gregorian calendar, and was November 11 to the Pilgrims who used the Julian calendar. 
The southern states had independently declared Thanksgivings of their own, untarnished by "Yankee" influences, but would later resent the new national Thanksgiving holiday after the war. 
President Lincoln declared a similar Thanksgiving observance in 1864 that was followed by President Andrew Johnson in 1865 and by every subsequent president.  After a few departures, on December 7, 1865 and November 18, 1869, the holiday was held the last Thursday in November.
Thanksgiving remained a custom, not sanctioned by law until 1941.
 In 1939 President Franklin D. Roosevelt declared November 23 as Thanksgiving, the next to the last Thursday that year, rather than the last Thursday of November, which could occasionally end up being the fifth Thursday and too close to Christmas for businesses.  Controversy arose, with  some Americans celebrating Thanksgiving on the 23rd and others on the 30th, including Plymouth, Massachusetts.
In 1940 the country was once again divided over "Franksgiving," as it was declared for November 21.  And again in 1941, Thanksgiving was declared for the earlier Thursday but President Roosevelt admitted that the earlier date, which had not proven useful to the commercial interests, was a mistake.