Today is Thanksgiving, in the USA, at least. Traditionally, the US has observed it a secular harvest festival.
The use of the turkey in the USA for Thanksgiving precedes Lincoln’s nationalization of the holiday in 1863. Alexander Hamilton proclaimed that no “Citizen of the United States should refrain from turkey on Thanksgiving Day”, but turkey was uncommon as Thanksgiving fare until after 1800. By 1857 turkey had become part of the traditional dinner in New England. 
Elsewhere in the country regional choices such as ham, chicken or other meats were the central dish. Turkey acquired its character as the national Thanksgiving entrée of choice in World War I (1918), when American men and women in the military dined on turkey, regardless of where they were stationed.