Turkey is the traditional dish for the Thanksgiving feast. In the US, about 280 million turkeys are sold for the Thanksgiving celebrations. There is no official reason or declaration for the use of turkey. They just happened to be the most plentiful meat available at the time of the first Thanksgiving in 1621, starting the tradition.
What a Downer!
Thomas Jefferson thought the concept of Thanksgiving was “the most ridiculous idea I’ve ever heard.”