Near the entrance to Amanohashidate, this welcome sign with "One of the three famous beauty spots of Japan" has been here for decades.

According to Japanese Wikipedia, the "Nihon Sankei" (Japan's Scenic Trio) label originated in 1643 by Hayashi Gaho (aka Hayashi Shunsai), a Japanese Neo-Confucian scholar who wrote a book mentioning these three sights. The expression "Nihon Sankei" was later coined in 1689 by another Japanese Neo-Confucianist scholar, Kaibara Ekken in his travel diary. So "Nihon Sankei" goes way back to the 17th century.

It's really amazing that it has stuck throughout these centuries even with Mt. Fuji not included. With Japan having so many places of beauty, it would be nearly impossible today for anyone to unilaterally declare any three sights as the "Best Three."

To the question of why it's always the best "three," the answer seems to be more complicated. It seems the Japanese have had numerical favorites for many centuries. Many odd numbers are favorites including one, three, five, and seven. This might sound familiar when you think about haiku and tanka poetry syllables, and the 7-5-3 coming of age celebration for kids. But the number "three" for "Best Three" has also stuck for centuries and still today.