About midway between Los Angeles and Las Vegas, in the middle of the Mojave Desert, sits a small abandoned body of water called Lake Dolores. It doesn’t look like much now, but it was once home to one of America’s first water parks.

Bob Byers built the area around the lake as a place for camping, then over the years added waterslides. Throughout the early 1970s and 80s, Lake Dolores was one of the most popular tourist attractions in Southern California. Although many of the rides, including a stand-up waterslide, seem dangerous by today’s standards, Byers’ creation helped pave the way for more elaborate parks.

On National Waterpark Day, celebrate by taking the plunge on a thrill seekers ride or cooling off in the lazy river.

Today we also celebrate: National Refreshment Day, Buffalo Soldiers Day, National Milk Chocolate Day, National Chili Dog Day, and National Intern Day.