Every Sunday in the 1960s and early 1970s, Cathy Douglas would hike the C&O Canal with her husband, U.S. Supreme Court Justice William O. Douglas.

The legendary jurist, who died in 1980, treasured the natural beauty of the towpath, which twists and winds its way 184 miles from bustling Washington to rural Maryland.

He was at home in the District one morning in 1954 when he read a Washington Post editorial backing a plan to build a highway over or along the historic canal. Douglas was incensed. He issued a challenge to the Post editorial writers: Walk with me the entire length of the canal, then tell me whether it should be preserved.

On March 20, 58 people — including Douglas, two editorial writers, the Post’s “country life” reporter, photographers, rival newspapermen and leading conservationists — set off from Cumberland, Md.

Only nine people completed the hike. But much publicity was generated, the newspaper reversed its stand and President Dwight D. Eisenhower eventually designated the canal a national monument.

Cathy Douglas Stoneis seen in Washington on Thursday. (Bonnie Jo Mount/The Washington Post)

This week, Cathy Douglas Stone returned to Washington to help commemorate the 60th anniversary of the hike and raise funds for the canal’s continued upkeep.

Five million people a year visit the canal, making it the ninth most popular park in the nation. In 1971, President Richard M. Nixon signed legislation to make the site a national historic park.

“It was extremely important to him,” Stone, who has remarried, said of her late husband. “As a resident of the District, he felt the work he did to protect the canal was part of his citizenship.”

Stone will help headline a “Park after Dark” celebration and fundraiser on Saturday at the historic Great Falls tavern along the towpath. Money raised will go to maintain the park, said Mike Nardolilli, president of the nonprofit C&O Canal Trust.

“We really are blessed to have it available to us,” said Dward Moore, president of the volunteers of the C&O Canal Association. “It’s a real treasure. . . . It’s a marvelous resource available to millions of people.”

The canal and its towpath were constructed in the early 19th century and used for almost 100 years to move coal, lumber and agricultural products to market. Improvements in railroad and other technology made the canal obsolete as a transportation system, but its appeal as a place of nature and beauty dates to Douglas’s day and beyond.

“The river and its islands are part of the charm,” he wrote. “The cliffs, the streams . . . the draws, the beaches, the swamps are another part. The birds and game, the blaze of color in the spring and fall, the cattails in the swamp, the blush of buds in late winter — these are also some of the glory of the place.”

C and O Canal

Stone, who serves on the board of the Wilderness Society and the Boston Harbor Islands National Recreation Area, said she and her first husband walked the towpath faithfully until 1972.

She recalled that Douglas often took solitary walks on the towpath “when he wanted to think deeply about a case” before the court.

“There’s a part of us as human beings, as a species, that needs to interact with the natural world,” Stone said. “It’s also part of a person’s spiritual development to interact with nature, beyond our everyday needs. It’s reassuring and refreshing.”

Stone was 23 when she married Douglas in 1966; he was 67. Now 71 and living in Boston, she makes a point of strolling along the canal whenever she comes to town.

“The bulk of our population lives in cities, and we’re removed from our natural roots,” Stone said. “Open spaces like the C&O Canal not only make cities livable, but they introduce children to nature.”

Every five years, the canal volunteers association recreates the Douglas hike. The two-week journey was condensed this year, however, because of cuts to the National Park Service budget.

And the history of the canal continues to evolve. In 2013, the hike-and-bike trail called the Great Allegheny Passage opened between Pittsburgh and Cumberland, extending the C&O Canal’s reach another 150 miles.

“Literally hundreds and hundreds of people” attempt to hike or bike the 334.5 miles that connect Pittsburgh to Washington, Moore said. “It’s an extremely popular route.”