In 1939 Thanksgiving was celebrated the last Thursday of the month.
That year the last Thursday was also the last day of the month, and Franklin Roosevelt and his cabinet were worried about the shortened holiday shopping season having a negative effect on retailers who were still trying to recover from the Depression, so he issued a Presidential order making it the next to last Thursday.
That set off something of a fight nationally. Most states agreed with the change, but over a dozen kept with the old schedule, so there were, for several years, TWO Thanksgiving Thursdays in the US.
It was finally resolved in 1941 when Congress agreed that the 4th Thursday of November would be the official Thanksgiving holiday.