For the past two decades, abandoned granite quarries near St. Cloud have attracted tens of thousands of visitors for swimming, cliff jumping, scuba diving and rock climbing.

Surrounded by flat farmland in central Minnesota, the 684-acre Quarry Park and Nature Preserve has tree-lined granite cliffs overlooking pools and draws an estimated 150,000 visitors each year, a turnout that keeps growing.

The park, the largest and most popular in Stearns County’s park system, is celebrating its 20th anniversary this month, hosting special activities from 10 a.m. to 2 p.m. June 16. The park also is getting more national recognition, named last month by the website Orbitz as having the best beach in Minnesota. In 2016, the park was featured on the Travel Channel’s list of top 10 “best swimming holes in the country.”

“The park keeps getting more and more popular,” Parks Director Ben Anderson said. “It’s not your typical pool.”

For decades, the Waite Park spot known as Hundred Acres Quarry was used to extract granite, helping St. Cloud get its “Granite City” nickname. The red granite from the quarries was used to build the Landmark Center and James J. Hill House in St. Paul.

But by the 1950s, the quarrying stopped and the abandoned water-filled pits became a hot spot for local residents to swim and party.

“Anyone who learned how to swim in the ’40s and ’50s learned in the quarries,” said Chuck Wocken, Stearns County’s parks director from 1975 to 2013.

Inspired by limestone quarries-turned-parks in Wisconsin, Wocken and other county leaders pursued buying the land, which had been privately owned. But everyone from the coroner to the county’s insurance company worried about safety and the environmental issues involved in turning quarries with high rock piles into a public park.

“You could imagine someone saying, ‘Are you nuts getting this as a park?’ ” Wocken said. “But there’s no reason the public shouldn’t get this view. The concept of reclamation for recreation was just getting traction.”

The county finally bought the land in 1992, opening the park six years later with trails through the woods, wetlands, prairie fields and billion-year-old bedrock. Over the years it also added land, and the park grew increasingly popular.

Now, a third of the park’s visitors are from the Twin Cities, with most — especially teens and college students — drawn to designated swimming spots in two of the 20 quarries.

“There isn’t a teenager in the metro area who doesn’t know about Quarry Park,” Wocken said. “On an 80-degree day, you can’t find a place to park. It’s the most refreshing swim you can come up with.”

Quarry No. 2 is 116 feet deep with high rocks for cliff jumping. It is so popular that the county opened a second swimming hole in Quarry No. 11, a former fishing spot that’s about 40 feet deep, adding a sandy beach, swimming platform and steps. Visitors walk a third of a mile to a half-mile to get to both areas.

There are no lifeguards, but the Stearns County Sheriff’s Office patrols the park (alcohol, tobacco and e-cigarettes are prohibited).

The park, which is the most popular of the county’s 16 parks and three recreational trails, brings in nearly $200,000 in fees each year (a daily permit is $5, a yearly permit is $20). Besides swimming, the park offers hiking and mountain bike trails, rock climbing and scuba diving in certain areas. Trout are stocked in seven quarries for fishing, and in winter months, the park has cross-country skiing trails.

“It’s just loaded with adventure recreation,” Wocken said. “The hazards are really the great attraction. It’s like the Badlands ... and the Boundary Waters right in an urban area.”