Like so many grand endeavors, the idea to buy a portion of Clapboard Island started on a lark.

Susan Gilpin, recently retired as pastor of a Congregational church, had set off in a boat from the Falmouth Town Landing with some friends. As they took in the leafy swath of Clapboard Island – the 35-acre expanse that shelters the boats moored at Falmouth – a friend mentioned that the property was on the market.

“I said, ‘We should buy it and turn it into a park,’ ” she said. “Then I started thinking, ‘That might actually be a good idea.’ ”

The offhanded remark touched off a 15-month $1.6 million fundraising effort spearheaded by Maine Coast Heritage Trust that is expected to be completed Aug. 15. If successful, the transaction will allow public access to the northeastern part of the island for the first time in more than a century.

Once Gilpin and members of the trust started exploring the feasibility of the project, Gilpin became even more convinced it was the right thing to do. With the woods, the beaches, the osprey and eagles – all an easy paddle from Falmouth and Portland – the island has a so-close-but-so-far-away character that makes it an ideal way to introduce people to the island and paddling.

“It’s quiet. you really feel like you’re in the wilderness. You look out on to the horizon, and feel like you can see into the infinite,” she said. “At the same time, you’re so close to Portland.”

​Gilpin approached the trust, which ​negotiated a deal with property owners to buy the 17-acre property on the northeastern part of the island for $1.4 million, and to raise another $200,000 for stewardship of the property.

Under the deal, the ​trust would purchase ​the acreage and ​open it to the public for daytime use. The western half of the island will remain private. An eight-bedroom house on that end of the island is on the market for $5.95 million.

The ​trust’s fundraising effort –​ aided by the Friends of Clapboard Island group that Gilpin headed –​ garnered support from 175 donors, ranging from $200,000 from the town of Falmouth to a $20 bill from a Boston contractor who’d never been to Maine but was captivated by the story of Clapboard, which Gilpin recounted when he asked about her “I love Clapboard Island” bumper sticker.

The trust’s acquisition of the eastern part of the island is a part its efforts to create a hub of islands in Casco Bay conserved for public use that offer wilderness experiences but are easily accessible from population centers such as Portland, Falmouth and Brunswick.

That hub includes the Goslings (the trust is now raising money to purchase them), Whaleboat Island (a 122-acre expanse acquired by the trust in 2002) and Lanes Island (a 28-acre island off Yarmouth given to the trust by the Gorman family in December).

A large part of the trust’s efforts to buy this portion of Clapboard Island involves the sale of the five-bedroom home, which is now on the market for $769,000. Even if they don’t sell the house – or raise the balance of the $175,000 in cash to reach their goal – they’ll go forward with the purchase, drawing the amount needed from the trust’s $3 million revolving loan fund.

Trust officials say that once the acquisition is complete, they hope the public will respect the private portion of the island. In the days ahead, trust workers will be putting up signs to mark what’s open to the public and what’s privately owned. The privately owned part includes two docks.

“We need visitors to respect the private landowners,” said Gilpin. “It’s a shared island and it only works if both parties are mutually respectful.”

That said, she’s excited about such a long effort coming to fruition.

“It’s amazing that it’s happening,” she said. “It’s so peaceful out there, and you feel so far away from all the things that your mind ordinarily goes in circles about.”