TIA, Marian Horvat: I am glad to acknowledge a note that a reader from Florida sent me bringing to my attention the fact that the first thanksgiving in the territory that today is the United States was not the one I featured in an article on this website several years ago. It actually took place in Florida five years before.
Thus, the first American Thanksgiving was neither at Plymouth Rock in 1621 nor in Texas on April 20, 1568 when Don Juan de Oñate crossed the Rio Grande and took formal possession of present day El Paso. This honor belongs to the city of St. Augustine, Florida, the first and oldest city of our present day United States. The landing of Captain General Pedro Menendez de Aviles and his fleet of soldiers and colonists – accompanied by priests – on the coast of Florida on September 8, 1565 has all the qualification to count it as the first official Thanksgiving Day in our country: Read article here.