Thirty years after the Thomas W. Harris planted the first commercial apple orchard in the Bitterroot Valley in 1866, the valley could boast it was home to the largest apple orchard in the world.

The Bitter Root Orchard Company’s 40,000 apple trees on 380 acres earned that honor.

What followed was a boom and bust cycle that saw more than a million apple trees planted in the Bitterroot by 1908. At its peak, the valley’s apple producers were shipping 637 boxcars of mostly McIntosh apples out on the rail by 1921.

Over the next two years, hailstorms would devastate most of the valley’s apple orchards.

The killing blow came in 1924 when a late spring frost decimated the crop by freezing buds on the trees. The three devastating years that followed brought a sudden end to the great Apple Boom of the Bitter Root.

That history hasn’t been forgotten.

For the last 40 years, the Ravalli County Museum has been hosting a celebration of that historic time when apples were king with an annual fall event that has come to be known as “The Biggest Bake Sale Under the Big Sky.”

This year’s McIntosh Apple Day is this Saturday, Oct. 5.

“It’s our 40th anniversary,” said Ravalli County Museum Executive Director Tamar Stanley. “It’s always been the museum’s major fundraiser of the year.”

The museum started the event as a way to preserve the agricultural heritage and the legacy of McIntosh apple of the Bitterroot Valley.

“It’s grown every year,” Stanley said. “Last year, we were able to get a fairly good count. There were more than 7,000 people who attended.”

On Thursday, a group of more than 30 volunteers gathered at Hamilton’s St. Francis of Assisi Catholic Church to make the 650 apple pies that will be sold Saturday morning after the event officially gets underway at 9 a.m.

The volunteers and members of Trapper Creek Job Corps culinary class were busy filling pie crusts with over 40 bushels of apples that had been peeled the day before.

At the end of a long table filled with empty pie shells, Kathleen Graler used both hands to reach into a bin filled with sweet-smelling sliced and sugared apples and then carefully placed what she gathered into the waiting pie crusts.

She’s been part of the pie-making brigade for more than a decade.

“It’s just plain fun,” Graler said. “All these people work together to put out so many pies to help the museum. I think we all do this because we love the museum.”

Sharon Gravert of Sacramento, California, offered her help after missing her flight back home. She was in Hamilton visiting her son and daughter-in-law, who are museum members.

“We were in the museum yesterday and ran into Tamar,” Gravert said. “She told us if we weren’t doing anything to come on by.”

It was the first time in her life that she had crimped the crust of apple pies. Gravert said it brought back memories of her grandmother.

“It’s just really been nice,” she said. “Next year I think I’m going to plan my vacation so I can be here again.”

Once the pies are put together the team of volunteers, they’re trucked to the Corvallis school kitchen and Hamilton’s Coffee Cup restaurant for baking.

“It’s really a community effort to make this happen every year,” Stanley said. “The pies are popular. They go pretty fast. Usually, by 1 p.m., we’re sold out. People need to get there a little early if they want to get one.”

But if they do want to sleep in, there will be opportunities to sample a range of apple-made products including the museum’s famous apple butter.

“Our apple butter is made from the freshest applesauce in the world,” Stanley said. “It’s a neat process to watch. The apple butter is sold in the quad as soon as it’s done cooking, sometime around noon.”

There will also be jars of apple chutney and caramel apples for sale during the event that ends at 3 p.m.

This year, the Montana Office of Tourism offered funding to help advertise Apple Day beyond the Bitterroot. The state also provided Apple Day-themed prizes that people can win by spinning a carnival-style wheel that will be set up in front of the museum’s entrance.

Those who attend the event can also take a spin around the block in a little electric train that traveled all from Colorado to help celebrate the 40th anniversary of McIntosh Apple Days.

Once the event comes to an end, folks might want to go take a nap to prepare for the second Ravalli County Museum sponsored fundraiser of the day that features apples in a liquid form.

The seventh annual Liquid Apple Night runs from 5 p.m. to 9 p.m. at the museum. Ticket holders receive a commemorative glass and free samplings of apple cider that's produced both locally and across the northwest. Local beers are also available.

“We have a burn barrel, twinkling lights and slow jazz music,” Stanley said. “It’s the perfect way to spend an autumn night.”