Armistice Day became a U.S. public holiday in 1939
“…It was on the 11th of November, 1918 that the Germans signed the Armistice to mark the end of the First World War , and therefore, the day became known as Armistice Day.
“U.S. President Woodrow Wilson first announced the Armistice Day in the year 1919. Subsequently, in 1926, the Congress of the United States passed a resolution to request the President to observe Armistice Day on the 11th of November with US flag celebrations. However, it was not until 1939 that [the] public holiday was declared on Armistice Day. An act that was approved in May, 1938 made November 11th of every year a legal holiday. ”
Excerpt from https://www.gettysburgflag.com/origins-of-veterans-day .
Later, the holiday name was changed to Veterans’ Day.