COCHRANE, Chile — An eagle soared over the lone house atop an arid hill in the steppes of Patagonia Park.
In the valley below, not far from the town of Cochrane, President Michelle Bachelet announced the creation of a vast national park system in Chile stretching from Hornopirén, 715 miles south of the capital, Santiago, to Cape Horn, the southern tip of South America, where Chile splinters into fjords and canals.
The park is the brainchild of Kristine McDivitt Tompkins and her husband, Douglas Tompkins, who founded The North Face and Esprit clothing companies, and starting in 1991, put $345 million — much of his fortune — buying large swaths of Patagonia.
As Ms. Bachelet spoke about the creation of the park network, Ms. Tompkins looked up and gasped, watching the eagle circling above the house, which she owns; águila, or eagle, was the radio call name of her husband.
Mr. Tompkins died at 72 in December 2015, after a kayaking accident in Patagonia. Months before, Tompkins Conservation, an umbrella group of conservation initiatives the couple directed, proposed a deal to the Chilean government: It would donate more than one million acres of their preserved and restored territory to Chile if the government committed additional lands and designated new parks to create a Patagonian national park network.
The Bachelet administration ended up contributing nine million acres, more than the couple had proposed, creating five new national parks and expanding an additional three. The deal was a rare victory for conservation efforts in a region where mining, logging and agriculture are increasingly threatening ecosystems and forests.
It was a partnership, Ms. Tompkins said in an interview, “a real model to do large-scale conservation and create national parks in a public-private way.”
The resulting 10 million-acre Patagonia National Park system is more than three times the size of the Yosemite and Yellowstone parks combined. It expands Chile’s national parklands by nearly 40 percent, enlarging the area of protection for pumas, condors, flamingos and endangered deer species.
By April 2019, the parks the Tompkinses donated will be run by Chile’s National Forestry Service; one will be renamed for Mr. Tompkins.
The parks are “good not only for Chile, but for the planet,” Ms. Bachelet said in an interview. “It shows that you don’t have to be a rich country to make these kinds of decisions. It only requires will and courage.”
Among some locals, though, reaction has been ambivalent. The mayor of Cochrane did not even attend the announcement in late January.
Getting to the site where the ceremony took place that windy morning required a seven-hour drive south from the closest airport, in Balmaceda, near the border with Argentina.
Along the way, unpaved roads wind through looming mountains, flanked by turquoise rivers and the seemingly endless General Carrera Lake.
Grasslands dotted with guanacos, a cousin of the camel, give way to sprawling steppes and forests, deep-blue waterways and majestic snow-capped mountains at the doorsteps of breathtaking ice fields.
“It is a wonderful coincidence to be here this day,” said John Rosenblum, the retired dean of the University of Virginia’s business school, who was visiting the park with his son the day of the announcement.
Mr. Tompkins traveled through Patagonia in 1961, when he was 18, an adventure seeker and rock climber. He bought his first lands there 30 years later — the 42,000-acre Reñihué farm in Los Lagos region, which he converted to organic agriculture.
The couple married in 1993, after Ms. McDivitt retired from the outdoor apparel company Patagonia, where she had risen to chief executive. They began “a very nomadic life looking at conservation projects in Chile and Argentina,” she said.
In partnership with the philanthropist Peter Buckley, the Tompkins purchased 208,000 more acres near the Corcovado volcano, south of Reñihué. They also bought more land further south, and large tracts in northeastern Argentina, which they are currently donating, in four stages, to the Argentine government.
Over the years, they continued buying property, largely from absent landowners, developing the more than 700,000-acre Pumalín Park, made mostly of temperate rain forests including the millenary alerce tree, a relative of the California redwood.
The valleys were used for ecological farming, and luxury cabins, camping sites, hiking trails and other infrastructure were built to open the park to the public.
Suddenly, the Tompkinses were at the center of national security concerns.
Politicians and the military argued that Pumalín Park, which crosses the narrow space between the Pacific Ocean and the Argentine border, cut the country in two, jeopardizing national sovereignty.
Business leaders and landowners accused Mr. Tompkins of impeding economic development. Nationalists said he was secretly creating a Zionist enclave in Patagonia.
Leftist parties were alarmed that an American businessman was buying big chunks of Chile. The Roman Catholic Church objected to the Foundation for Deep Ecology, which Mr. Tompkins founded in 1990 in San Francisco, saying it sought population-control.
Mr. Tompkins was vilified in the conservative news media, interrogated by congressional commissions and threatened with deportation.
Then, in 2005, the Tompkinses began donating land to the Chilean government to create a park. That same year, the government designated Pumalín a nature sanctuary.
By then, Tompkins Conservation had bought another large parcel of land, a 764,000-acre sheep farm in Valle Chacabuco, which it named Patagonia Park. Local ranchers and farmers objected to the purchase, saying their traditional livelihoods were being disrupted.
With the help of international donors and partners, the group took down more than 400 miles of fencing, removed 25,000 sheep and again built high-end lodges, campgrounds, hiking trails and roads, developing programs to restore natural ecosystems and to reintroduce wildlife to their natural habitats.
“There is something about the expanse of Patagonia, a kind of haunting soulfulness to it that affects you physically,” Ms. Tompkins said the day the new park network was announced. “Few places like this one grab you and hold on to you like it happened to Doug and I.”