President George Washington signed that proclamation and declared Thursday, November 26, 1789, as the first national Thanksgiving Day.

As time passed, the holiday was celebrated sporadically.

A magazine editor named Sarah Josepha Hale helped organize a movement to make Thanksgiving a national holiday. Every year from 1846 to 1863, Mrs. Hale printed an editorial in her magazine urging the government to establish this holiday. The date Ms. Hale suggested was July fourth. It was a logical date, but as interest in this holiday grew, a November date was proposed.

In 1863, in the middle of the Civil War, President Abraham Lincoln set aside the last Thursday of November as a day of national “Thanksgiving and praise to our beneficent Father who dwelleth in the Heavens.”

Lincoln declared another Thanksgiving Day the following year, as did his successor, Andrew Johnson. Other presidents followed the new tradition annually with the holiday landing in December for a few years.

The date for Thanksgiving was again changed briefly in 1939 to the third Thursday of November but public opposition caused the U.S. Congress to establish the fourth Thursday as the holiday date. President Franklin Roosevelt signed a bill on November 26, 1941, that finally established the fourth Thursday of November as our national Thanksgiving Day.

A time of Thanksgiving is not just a national holiday, it is a biblical imperative. In the Old Testament, God’s people celebrated a number of yearly feasts. The Feast of Unleavened Bread commemorated the Israelites’ deliverance from bondage in Egypt. The Feast of Weeks was for the purpose of dedicating the first fruits of the new crops. The Feast of Booths was a feast at the end of the harvest season to celebrate God’s abundant provision. These were not optional events but they were written into God’s law. God knows it is important for us to set time aside to reflect on God’s goodness. Our faith grows as we remember how God has provided for us in the past.

Oh give thanks to the Lord; call upon his name; make known his deeds among the peoples! Sing to him, sing praises to him; tell of all his wondrous works!... Remember the wondrous works that he has done, his miracles, and the judgments he uttered, Psalm 105:1–2,5 (ESV)

(History taken from Thanksgiving: A Time to Remember by Barbara Rainey)