Tripods are usually fine, but not at crowded viewpoints.
Yes, there are restrictions — basically, don’t block foot traffic.
Most national parks and state parks allow tripods for personal photography. The catch is where you set them up. At popular viewpoints, boardwalks, and narrow trails, park rangers will ask you to move or put it away. The rule is never impede the flow of people.
Some parks (like Yosemite or Grand Canyon) have specific viewpoint hours where tripods are banned during peak times. And if you’re shooting commercially, you likely need a permit, even with a tripod. But for a regular person with a standard camera? You’re fine as long as you’re not that person taking up the entire platform for thirty minutes.
Leave the tripod in the car for the main overlooks if it’s a busy day.
