During the Civil War Massachusetts Governor John Albion Andrew declared a day of fasting “Humiliation and Prayer” in April 1861.
He also proclaimed a “Day of Thanksgiving and Praise” later that year. The language would be familiar to Puritan settlers two hundred years earlier.
When things went wrong, or a difficult challenge loomed, Pilgrims and Puritans declared a day of fasting. With good fortune, they held a day of thanksgiving. From a modern viewpoint the days might seem similar, with long hours in the meetinghouse, followed by a light meal on fast days, and a more celebratory meal on days of thanksgiving. The holiday evolved from this tradition.