When Capt. Moses Harris and his troops from Company M, First Cavalry marched into Yellowstone in August 1886, the world's first national park was in chaos.

Fourteen years of corrupt or incompetent management by political appointees threatened its existence. There had been little protection of the park’s natural wonders. Congressional funding was an afterthought. But by the time the Army handed Yellowstone's administration to the fledgling National Park Service 30 years later, it had set in motion policies and procedures that would serve as the model for park management for decades to come.

Would there even be a national parks system today without the cavalry's stewardship of Yellowstone?

"It’s been debated. Nobody knows," says Lee Whittlesey, who has worked at Yellowstone for 35 years and been the park historian since 2000. "I would submit the Army went a long way towards protecting an area that had very little protection and turned it into a place of relative tranquility, where tourists could enjoy it while also protecting its wonders.”

Without that intervention, he adds, "Congress might have thrown up its hands and turned it over to private settlement. There certainly were a fair number of voices yelling for that in Congress."

Yellowstone was designated as a national park in 1872, and the Department of the Interior was charged with the “preservation, from injury or spoliation, of all timber, mineral deposits, natural curiosities, or wonders within said park, and their retention in their natural condition.”

But prior to Harris' arrival, rampant poaching so endangered bison, elk, deer and other animals that Buffalo Bill Cody had written a letter to the New York Sun pleading for protections. Timber cutting and grazing left swaths of land devastated. Fires set by angry settlers—there were three large blazes ongoing at the time of Harris's arrival—destroyed acre after acre. Vandals sliced fragile pieces of ornate travertine with axes to sell as souvenirs and signed their names on geyser formations.

Congress was so angry with the inept administration of the park that it refused to allocate funds, according to Whittlesey. As part of a compromise agreement funding the park, control shifted to the military, under the direction of the Department of the Interior.

The first troop of about 60 men was 50 more than had covered the 2.2 million acres of the park under civilian administrations. Their numbers grew to two troops, then three and eventually four by 1910, as visitors to the park increased from 500 in 1880 to more than 19,000 in 1910.

Within two months of arriving in 1886, Harris reported to the Secretary of the Interior that the forests and the game "has been well protected," but progress was slow preventing vandalism to the geysers.

"It may be said without exaggeration that not one of the notable geyser formations in the Park has escaped mutilation or defacement in some form," he wrote, noting the lack of effective rules, regulations and especially penalties. “All sorts of worthless and disreputable characters are attracted here by the impunity afforded by the absence of law and courts of justice.”

Early military commanders at Yellowstone kept a close watch on geysers. They charted eruptions. Soldiers stood sentry, forcing those caught signing their names to scrub off the offending graffiti.

Despite the early optimism, poachers proved to be an enduring problem, partly because there were no significant penalties on the books. Harris created extra-legal measures, Whittlesey says, confiscating their possessions and locking them in the guardhouse for weeks before expelling them from the park as his only recourse.

Only in 1894, five years after Harris left Yellowstone, did Congress heed his request to pass a “stringent law." Soldiers caught a local poacher named Edgar Howell standing over the carcasses of bison he slaughtered for their scalps, which fetched $300 apiece. A photographer and writer from Field & Stream happened to be in the park that day, and their long story about the crime prodded Congress to rush through a bill.

Whittlesey notes that the military did manipulate nature, stocking trout, for instance, and bringing in bison from Texas and Montana to breed when the park's herd dropped to only 23 animals in 1902. But acting superintendents also pushed back against projects they saw as despoiling the “natural condition.”

Capt. F. A. Boutelle succeeded Harris and soon clashed with his superior in Washington over the proposed construction of an elevator that would transport tourists to the bottom of Yellowstone's Grand Canyon for a better view of the 308-foot Lower Falls. Boutelle not only objected to the elevator, but any commercialization of the park. He won. Washington officials revoked permission to build the elevator, and his objection to commercialization became an enduring national parks philosophy.

The military administration at Yellowstone proved to be a model for the early management of Yosemite, Sequoia and Kings Canyon National Parks in California. With the creation of the National Park Service in 1916, the soldiers withdrew.

Naturalist John Muir noted his appreciation for the military’s stewardship in his 1901 book Our National Parks: "The national parks are not only withdrawn from sale and entry like the forest reservations, but are efficiently managed and guarded by small troops of United States cavalry,” he wrote, calling it a refreshing thing compared to the ruthless destruction in adjacent regions.

“In pleasing contrast to the noisy, ever changing management, or mismanagement, of blundering, plundering, money-making vote-sellers who receive their places from boss politicians as purchased goods,” he added, “the soldiers do their duty so quietly that the traveler is scarce aware of their presence."