Which of the following is a recognized U.S. holiday?

Christmas is recognized as a federal holiday in the United States, celebrated on December 25th each year. It commemorates the birth of Jesus Christ and is widely observed not only culturally and religiously but also includes various traditions such as gift-giving and festive decorations.

The other options—Valentine's Day, Earth Day, and Mother's Day—while celebrated in the U.S., are not designated as federal holidays. Valentine’s Day, occurring on February 14th, focuses on romance and affection; Earth Day, celebrated on April 22nd, promotes environmental awareness; and Mother's Day, honoring mothers, takes place on the second Sunday in May. These occasions do not carry the same national recognition and public observance as Thanksgiving or Independence Day, making Christmas the correct answer in this context.