According to USPS:
In observance of Feb. 7, 2008 Lunar New Year holiday, the U.S. Postal Service introduces a new series of Lunar New Year stamps that will continue through 2019. Beginning with the Year of the Rat in 2008, stamps issued in consecutive years will include the Year of the Ox, Tiger, Rabbit, Dragon, Snake, Horse, Ram, Monkey, Rooster, Dog and Boar.
With the 31st stamp in its Black Heritage series, the U.S. Postal Service honors Charles W. Chesnutt (1858-1932), a pioneering writer recognized today as a major innovator and singular voice among turn-of-the-century literary realists who probed the color line in American life. In novels such as The Marrow of Tradition and short stories such as those collected in The Conjure Woman, he probed the color line in American life.