According to the passage, in 1621 Thanksgiving was celebrated for______.

When we think of Thanksgiving today, images of football, pumpkin pie, parades, and turkey dinner complete with cranberry sauce come to mind, as well as plans for a Black Friday shopping holiday the following day.(18-1)Of course none of these items were present back in 1621, when the Indian people and the Pilgrims sat down together to give thanks for nature’s bounty.(18-2)Although the celebrants at this particular meal didn’t even call it "Thanksgiving" , this particular harvest feast is the one after which we model our modern-day Thanksgiving celebrations. After 1621, future Thanksgiving celebrations occurred at various times throughout the year. George Washington declared a feast of Thanksgiving in 1789, and presidents issued similar yearly proclamations after that.(19)During the Civil War, poet Sarah Hale started a campaign to celebrate the holiday on the same day throughout the country. President Abraham Lincoln saw it as a way to unite the country, and in 1863 he proclaimed a national Thanksgiving celebration on the last Thursday in November. It was changed from the last Thursday to the third Thursday by Franklin Roosevelt in 1939 as a way to lengthen the Christmas shopping holiday. In 1941, Roosevelt finally changed the date to the fourth Thursday in November, proclaiming it a Federal holiday in 1941.