The Lake Arthur Regatta is this weekend. This popular annual event attracts thousands for the sailboat races, fishing tournament, hot air balloons, hiking, swimming, what’s billed as the “World’s Premier Canine Aquatics Competition” and, of course, fireworks. But how many who attend know that Lake Arthur is a recreation of an ancient glacial lake? Or that it took 11 months to fill? Or that an old highway runs under the water?

It’s the third largest state park in Pennsylvania, and now a new book, “Moraine State Park,” tells its story, mostly using photographs.

Moraine State Park is in Butler County, less than an hour north of Pittsburgh. It was established 1970, but author Polly Shaw says its history goes back much further.

“There was a glacier, in the Pleistocene era. It receded 20,000 or 18,000 years ago,” Shaw says. “The ‘moraine’ refers to that edge of the glacier.”

A lifelong resident of Butler County, Pennsylvania, Polly Shaw is a retired teacher, history enthusiast, and longtime state park volunteer. Photo: Kara Holsopple

That edge is where rocks and debris were deposited, and it’s just north of where the park is now. A glacial lake was formed, because north-flowing waters were impounded by the glacier, Shaw says. When the glacier receded, and the lake evaporated, a flat land mass was created, which is distinct from the surrounding hills of western Pennsylvania.

LISTEN: “Moraine State Park’s History Goes Way Back”

Shaw is a dedicated and animated storyteller when she talks about the park. And she’s uniquely qualified to do it. Before retiring, she spent 37 years teaching elementary school in the area, is a lifelong resident of Butler County, and has been volunteering at nearby McConnell’s Mill State Park for 20 summers. Shaw sifted through archival photographs from the park office, and even took a few of her own to take readers through Moraine State Park’s past and present. It’s part history book, part guide book.

Now a hiking and equestrian path in Moraine State Park, this was once part of the route for the Western Allegheny Railroad, which hauled coal and limestone out of the area. (Photo: Polly Shaw/Arcadia Publishing)

A photograph of green park trail, used for hiking, horseback riding and snowmobiling, hints at its previous life as a route for the Western Allegheny Railroad. Before the line closed in 1939, trains carried coal and limestone from the area to steel mills. There were hundreds of small oil wells in the area, too.

“The land was scarred. The land was damaged in many ways,” says Shaw. “The land was ready to be repurposed.”

Frank Preston, an engineer from England, saw the potential for a park. A black and white photograph in the book shows Preston, with a bird of prey perched on his arm, standing in front of a tree with his wife, Jane,and their dog.

“His vocation was being a glass technologist, but his avocation was in botany, ornithology, and geology,” Shaw says.

Frank Preston was an English engineer and ecologist who helped found the Western Pennsylvania Conservancy. Moraine State Park was his brainchild. He’s pictured here with his wife, Jane. (Photo courtesy of Polly Shaw/Arcadia Publishing. Credit: Preston Park/Butler Township)

Preston originally came to Butler County in the 1920s to work at Standard Plate and Glass. Eventually he started his own business, and when he had time, explored the local landscape. Shaw says he mapped out the shoreline of the ancient glacial lake, which was similar to the glacial formations in his native Leicester. In 1946, he met fellow outdoors enthusiast, and amateur geologist, Edmund Watts Arthur. Arthur was an attorney from Pittsburgh who also loved poking around in Butler County. Their mutual interest began a friendship and partnership that lasted only two years, when Arthur suddenly died. Just a few months after his death, Preston gathered influential people from Pittsburgh and the local area on a piece of property he owned in Butler County. He laid out the idea for Moraine State Park, as well as a recreation of the glacial lake, which was named Lake Arthur.

The heart of the book details how Preston, a founder of the Western Pennsylvania Conservancy, and others, convinced the inhabitants of the tiny village of Isle to move and had the state reroute a highway so that the park could be built. Photographs document the damming of Muddy Creek, and how it took 11 months to fill Lake Arthur. Old US 422 is under the current lake. As it filled, some people drove their cars out onto the roadway as far as they could. An old photograph from the period makes it look as though they are floating on the water.

The last half of Shaw’s book celebrates the fruits of all of that labor. People sail, kayak and fish on Lake Arthur, which at 3,225 acres is the largest manmade lake within the state. Trails within the park are used in all seasons, and Moraine State Park is habitat for wildlife from bears to bats. Osprey were reintroduced to the area in 1993, and they’ve thrived with help from the Moraine Preservation Fund.

Sailing is a popular activity on Lake Arthur. Photo courtesy Polly Shaw/Arcadia Publishing. Credit: John Keck.

Once a year, Saw says she and her family pack up a picnic, rent a pontoon boat and enjoy putting around on the water, and she and her grandson have been on every trail in the park.

“I used to hike a lot further, but my feet don’t seem to want to take me as far as they used to,” she says.

She’s certainly not done with Moraine, but Shaw is moving on for her next book. She’s taking on McConnells Mill State Park, where she gives tours at the old grist mill. But it’s all in the family. The parks are under the same management.