Which of the following is NOT a national U.S. holiday?

Halloween is not a national U.S. holiday. While it is widely celebrated across the country on October 31st, it does not have the status of a federal holiday. The federal government recognizes specific national holidays, which are designated by law and include days like New Year's Day, Independence Day, and Memorial Day. These holidays are recognized across all states, and federal employees are typically given the day off, while Halloween, despite its popularity and cultural significance, does not have this designation. This distinction helps clarify the difference between widely celebrated cultural observances and official federal holidays recognized by the government.