MSN.com echoes a Vox.com column about how the turkey got selected as the entree for the Thanksgiving feast. Spoiler alert. It did not start with the Pilgrim colony in MA, they probably ate venison.
Out of my family history, I’ll add something the article doesn’t mention. During World War II the US had meat rationing for civilians. Big roasts and hams were basically unavailable, unless you knew someone in the butchery business.
Curiously, turkeys were not rationed; something of which one of my uncles took full advantage. He and his wife raised and slaughtered hundreds of turkeys annually in rural SoCal, with the aid of a cluster of neighborhood women who earned money for Christmas shopping by ‘dressing’ the birds for cooking.
Uncle sold the turkeys from a store at their farm throughout the Thanksgiving - Christmas - New Years - Easter season during and briefly after the war. When the production of beef and pork caught up with demand, the market for turkey contracted to basically Thanksgiving and Christmas.
I conclude that among the factors making turkey the entree of choice for Thanksgiving, rationing during WW II must be included.