Thanksgiving, or Thanksgiving Day, is a traditional North American holiday and is also a form of harvest festival. While many think Thanksgiving originated in the United States, in fact it was first celebrated in what would become Canada in the late 1500s. It wasn't celebrated until the early 1600s, roughly estimated 1621 when the pilgrims and Native Americans gathered, in what would become the United States.
Since it's very first gathering Thanksgiving has remained unchanged. It is a holiday that's name says exactly what it is, a time for giving thanks.
People generally give thanks with feasting and prayer for the blessings they have received during the year. The first Thanksgivings were for thanking God for plentiful harvests. For this reason, the holiday is associated with fall - a time of harvesting the crops.
In the United States, Thanksgiving is usually a day celebrated with big dinners and family reunions. Thanksgiving is also a time for religious reflection, church services and prayer. The last Thursday in November was proclaimed the National Thanksgiving holiday by Abraham Lincoln in 1863. He proclaimed it "a day of thanksgiving and praise to the beneficent Father." Thanksgiving was celebrated on that date for 75 years until President Roosevelt set the day one week earlier in 1939 so as to lengthen the shopping period between Thanksgiving and Christmas to help businesses. Congress finally ruled in 1941 that the fourth Thursday in November would be the legal National Thanksgiving Day holiday.