Separatist father William Bradford explains the events which led to a celebration of the First Thanksgiving in the English colonies in America. It was in grateful response to God for a specific providential deliverance in the year that this day was held at Plymouth Colony, Massachusetts in 1623.
“I may not here omit how, not withstand all their great pains and industry, and the great hopes of a large cop, the Lord seemed to blast, and take away the same, and to threaten further and more sore famine unto them. By a great drought which continued from the third week in May, till about the middle of July, without any rain and with great heat for the most part, insomuch as the corn began to wither away though it was set with fish, the moisture whereof helped it much. Yet at length it began to languish sore, and some of the drier grounds were parched like withered hay, part whereof was never recovered. Upon which they set apart a solemn day of humiliation, to seek the Lord by humble and fervent prayer, in this great distress. And He was pleased to give them gracious and speedy answer, both to their own and the Indians’ admiration that lived amongst them. For all the morning, and greatest part of the day, it was clear weather and very hot, and not a cloud or any sign of rain to be seen; yet toward evening it began to overcast, and shortly after to rain with such sweet and gentle showers as gave them cause of rejoicing and blessing God. It came without either wind or thunder or any violence, and by degrees in that abundance as that the earth was throughly wet and soaked and therewith. Which did so apparently revive and quicken the decayed corn and other fruits, as was wonderful to see, and made the Indians astonished to behold. And afterwards the Lord sent them such seasonable showers, with interchange of fair warm weather as, through His blessing, caused a fruitful and liberal harvest, to their no small comfort and rejoicing. For which mercy, in time convenient, they also set apart a day of thanksgiving.”
William Bradford, Of Plymouth Plantation, Alfred A. Knopf, ed., Borzoi Books, pp. 131-132.