Yes, the Gateway Arch in St. Louis is specifically engineered to sway in the wind to prevent structural failure. According to the National Park Service, the Arch is designed to deflect up to 18 inches in either direction from its center point without any permanent damage. However, it takes an extreme force—equivalent to a 150 mph wind—to reach that maximum 18-inch sway. Under more typical conditions, such as a 50 mph wind, the top of the Arch only moves about 1.5 to 2 inches. Visitors inside the observation deck at the top often report that even a one-inch movement "feels" much larger due to the height and the enclosed space of the small windows. The Arch’s "legs" are aligned on a north-south axis, meaning most of the sway occurs east-to-west. This flexibility is a hallmark of modern skyscraper and monument engineering; if the structure were perfectly rigid, it would be much more likely to crack or fail during the intense thunderstorms and high-wind events common in the American Midwest.