Today, May 13, marks a significant date in American history, one that echoes the struggles and triumphs of the nation's past. On this day in 1864, President Abraham Lincoln issued a proclamation declaring the last Thursday in May to be Thanksgiving Day, in an effort to unite the country during the tumultuous Civil War era. However, it wouldn't be until 1938 that Congress would officially establish the holiday as we know it today, with Franklin D. Roosevelt moving it to the fourth Thursday of November. As Americans gather with loved ones to celebrate the holiday, they may not be aware of the pivotal moment in history that paved the way for the modern tradition of Thanksgiving.