Historical marker #1801 in Whitley County celebrates the natural phenomenon of the moonbow at the Cumberland Falls.
Officially becoming a state park in 1931, the Cumberland Falls State Park sits on the Cumberland River with a large waterfall bordering Whitney and McCreary County. The falls are 125 feet wide with a drop of 68 feet and gained the nickname the “Niagara of the South.” In the right nighttime conditions, the Cumberland Falls create a natural occurrence unlike anything else in the Western Hemisphere, the moonbow.
The Cumberland Falls sit at an atypical angle; they face north and flow north. This positioning allows light to reflect off the moon to create a rainbow in the dark. This optical phenomenon is known as a moonbow or lunar rainbow. Several factors must come together for the moonbow to appear including specific water temperatures, rising mist, clear skies, water clarity, and particular wind speed and direction. The moonbow can happen two days before, on, or after a full moon.
The Cumberland Falls lunar rainbow is strongest when the moon is lowest in the sky. This time occurs between dusk and midnight. The higher the moon rises, the lower the moonbow sinks until it disappears from the view on the Upper and Lower Overlooks. The Cumberland Falls moonbow is special because it appears on a fairly predictable schedule. Other moonbows appear in the Western Hemisphere but they cannot be calculated like the one at the Cumberland Falls. The only other predictable moonbow occurs at Victoria Falls in Zimbabwe, Africa.
The moonbow at the Cumberland Falls has attracted visitors for generations. One place that visitors stayed was at the Moonbow Inn. The inn was built sometime in the late to mid-nineteenth century. H. C. Brunson acquired the property later and the hotel became the Brunson Inn. In the 1930s, around when Cumberland Falls became a state park, the property was renamed the Moonbow Inn, for the famous natural attraction nearby. In the 1940s, the Moonbow Inn burned down. While the inn does not exist, people still frequently travel to Cumberland Falls State Park at night to experience the moonbow.