During the summer of 1861, a 35-year-old photographer called Carleton Watkins strapped almost a tonne of camera equipment on to mules and rode the long, largely untravelled trail into California's Yosemite Valley. Three years later, the 30 images he captured of the valley's vertiginous ravines, cascading waterfalls and monumental trees had directly inspired Abraham Lincoln – more than 2,000 miles away in Washington DC and otherwise absorbed by the civil war – to sign the legislation needed to secure in perpetuity the wilderness "for public use, resort, and recreation".

For the first time anywhere in the world, a government had created what was, in effect, a national park. With mining and logging companies already eyeing up the valley, which had only been "discovered" a decade earlier, the "Yosemite grant" was a gesture that jump-started the conservation movement and helped to push against the "manifest destiny" – the common sentiment in America at the time that it was a settler's God-given right to fully exploit the natural resources they found "out west".

Watkins's critical role in the early history of environmentalism – particularly his 1861 images of Yosemite – is rarely recognised today, even within the movement itself. But, on the 150th anniversary of his landmark expedition, the J Paul Getty Museum in Los Angeles, which holds so many of his original prints, has published for the first time a complete collection of all the "mammoth photographs" he took throughout his eventful life.

The book – which contains 1,273 images and costs almost $200 – is the culmination of a career-long Watkins obsession by Weston Naef, who, until his retirement two years ago, was the curator of photography at the Getty Museum. He ranks Watkins alongside the other early photographers of that age, such as Eadweard Muybridge and Julia Margaret Cameron, but believes he had a unique influence.

"Watkins achieved a poetic beauty in his 1861 Yosemite series that surpassed in quality and size any other landscape photographs made in America to that time," Naef says. "The photographs elicited in people who saw them a belief that what he showed must be protected from harm, and as such they are the very beginning of a movement that had not yet been named. Early proponents of the drive to protect and preserve natural resources, such as Frederick Law Olmstead and John Muir, studied Watkins's photographs and admitted to their influence. John Muir later spent many hours with Watkins and literally walked in his footsteps by retracing the photographer's travels."

Today, Yosemite is one of the most visited tourist destinations in the US. Visitors flock to see its world-famous natural features, such as the Vernal Falls, El Capitan, Cathedral Rock, Half Dome and Mirror Lake. But Watkins's images captured the valley in an ethereal, timeless state before human interruption. This is how his images were first perceived, anyway. (The Ahwahnechee, the Native American tribe that had lived in the valley for centuries, had been driven out in the early 1850s.) When they finally reached the east coast a year later and were displayed at the Goupil Gallery on Broadway, New York, in December 1862, the New York Times described the "wonderful scenes" displayed in Watkins's "splendid" photographs as a "a valuable contribution to art". It added: "As specimens of the photographic art they are unequalled, and reflect great credit upon the producer, Mr Watkins. The views of lofty mountains, of gigantic trees, of falls of water which seem to descend from heights in the heavens and break into mists before they reach the ground, are indescribably unique and beautiful. Nothing in the way of landscape can be more impressive or picturesque."

For the very first time, visitors were able to see a real representation of the much-discussed valley, rather than rely on written accounts, or an artistic impression.

Lincoln did not view the photographs in New York, though. Conclusive proof is lacking, but Naef believes there is enough circumstantial evidence to suggest that John Conness, the Californian senator, showed his own personal set of Watkins images to Lincoln in Washington DC. Conness was allied to a small collective of wealthy, influential Californians who sought to protect Yosemite, not from exploitation per se – as environmentalists might see it today – but to guarantee its pristine condition in order to attract tourists to the state and to bolster California's national standing. Other natural wonders, such as the "Big Trees" grove of giant sequoias found by gold miners in nearby Calaveras county a decade earlier, were already starting to fuel a fledgling tourism industry by creating media interest all around the world.

The only identifiable human to feature in Watkins's set of 1861 images is Galen Clark, the man many still claim to be the "first conservationist". He can be seen in one image standing at the base of the "Grizzly Giant", a huge sequoia located in Mariposa Grove that marked the starting point for any journey into Yosemite Valley. (Another image of the same tree shows four men at its base, presumably members of Los Mariposa mining estate, which – somewhat ironically – had hired Watkins to help survey the area.) Clark, like Watkins himself, had travelled to California during the gold rush a decade earlier, but after catching tuberculosis he moved to the mountain air of the Sierra Nevada and built a cabin at Mariposa after being both humbled and inspired by the 300ft-tall, 2,000-year-old trees. From 1856 onwards he led the campaign to have the area protected and soon managed to gain Senator Conness's crucial support. Clark acted as a guide for anyone entering the area and even offered humble accommodation. He soon became known as the "Guardian of Yosemite Valley" and Watkins photographed him not just on his 1861 visit but also on many of the subsequent seven visits he made as his reputation grew and he established a studio in San Francisco selling images of the valley.

Naef makes a convincing case that Watkins first visited Yosemite a few years before 1861. In 1859, an Englishman called James Mason Hutchings, who did so much to spread the word of California's natural curiosities to "lovers of the marvellous", published a 10-part series about Yosemite in his popular publication called Hutchings' Illustrated California Magazine. It included engravings of the valley that, according to Naef's expert eye, bear all Watkins's hallmarks. Naef is sure they must have been directly inspired by now lost images captured by the photographer. (Much of Watkins's archive was destroyed during the San Francisco earthquake of 1906.)

Watkins's style is certainly distinctive. He typically preferred high vantage points for his panoramic landscapes, which enabled him to develop a composition looking down on his subject. Given that his "mammoth camera" was so heavy and cumbersome to both carry and operate, it shows the lengths he would go to for his art, especially when some of the vantage points he favoured are a day-long journey, even today. Other characteristics of his images are the tell-tale shadows cast by early morning or late afternoon sunlight. He also liked to centre his images with a distinctive feature in the foreground such as a rock or tree and then frame it with either middle or far-distance trees or cliffs on both the left and right-hand side. And he kept returning to the same vantage points on each visit, meaning his archive allows historians and scientists to see how Yosemite changed over the decades Watkins was photographing the area.

"Watkins's visual genius was in knowing exactly where to position his camera to maximise the potential of each subject," says Naef. "His viewpoints were consistently so perfect they set the example for all future representations by those who walked in his footsteps – even Ansel Adams, the celebrated 20th century environmental photographer – and his viewpoints became conventions long after he was forgotten as their inventor. Like the painter Paul Cézanne, he structured his compositions as a network of tightly woven visual relationships that connect different parts of the picture as a delicate surface pattern."

Watkins – who was born in 1829 in upstate New York – developed an international reputation in 1867 when his Yosemite images were displayed at the Exposition Universelle in Paris, winning him a gold medal for landscape photography. Some art historians believe Gustave Courbet, the French realist painter, was inspired by seeing the photographs, as had been the case with Albert Bierstadt, the American landscape painter, who saw them in New York at the Goupil, causing him to leave for Yosemite.

But the Paris exhibition was where Watkins's run of bad fortune began. Mistaken media reports misattributed his medal-winning images to a rival photographer called Charles Weed. And after he ran up debts trying to bolster his studio in San Francisco he was forced to auction off his photographs, meaning they were reprinted without his name by the new copyright holder. Other photographers soon began to ape his now famous compositions of Yosemite and, even though he worked hard travelling throughout California capturing scenes of the new railroad and a fast-expanding San Francisco, he remained in penury for the rest of his life. Four years after the fire caused by the 1906 earthquake had destroyed much of his legacy, he was committed to the Napa State hospital for the insane, where he died in 1916. It was only in 1975, when Naef curated a photography exhibition entitled "Era of Exploration" at the Metropolitan Museum in New York, that Watkins's reputation once again began to rise.

"Carleton Watkins is to photography what Cézanne and Van Gogh are to painting," Naef says. "This man was probably the greatest American artist of his era, and hardly anyone has heard of him."

But – his artistic legacy withstanding – it is hard to consider the birth of the environmental movement without mentioning Watkins and the rippling, far-reaching influence of his 1861 images of Yosemite. All that came after – Lincoln's signing of the Yosemite grant, Muir's nature writing, the founding of conservation groups such as the Sierra Club – can be traced back to the intake of breath when his images were seen for the first time.

Carleton Watkins: The Complete Mammoth Photographs, by Weston Naef and Christine Hult-Lewis, is published by Getty Publications, $195.

Go to our gallery of Watkins photographs

• This article was amended on 10 January 2012 because it referred to Vernon Falls instead of Vernal Falls.