A book exactly tackling the smoke problems you speak of is called Age of Smoke by Frank Uoketter. He argues that there was a long history of slow and steady environmentalist action on the problems of industrial smoke in both Germany and the US - and that the environmental revolution that occurred in the 1970s on a both legislative and societal levels in some ways derailed the progress that had been made! Essentially, it created and oppositional relationship between industry and state over environmental issues, where before there had been cooperation and compromise - which had been, well, slow and steady at best in its progress. It's a provocative argument but I think that its point essentially gets at the answer to your question.

Why the modern environmentalist movement, with its specific constellation of approaches and beliefs (federal legislation, litigation against corporations, anti-industrial and anti-consumerist attitude, etc. etc. etc.) occurred in the 1960-70s is a separate question from when and why what we would call environmentalist agendas occurred in the past at large - because they did!

In the Progressive Era, for instance, women like Jane Addams and Florence Kelley, more famous for their work in settlement houses and immigrants, also tackled a large number of 'quality of life' environmentalist issues like urban pollution and sanitation - and there were many many many men working on designing municipal water systems that provided people with unpolluted water in the late 19th century. And don't forget the conservation movement of the early twentieth century to protect forest and other resources!

[And for the record, a number of people have suggested a number of other things contributing to the twentieth century environmentalism ranging from Adam Rome's suggestion that suburbanization played a strong role (see his book about Earth day too!) to Thomas Robertson's identification of Malthusian paranoia as crucial motivator.]

EDIT: A great source about women and municipal housekeeping that incorporates a look at their environment-improving agendas is Seeing With Their Hearts by Maureen Flanagan. For environmental histories of early urban development highlighting male achievements, see almost anything by Martin Melosi but I like Garbage in the Cities best. Also I've provided links for the work of Adam Rome and Thomas Robertson!

As /u/TheShowIsNotTheShow suggests, the roots of the modern environmental movement are in the Progressive Era, but there was a much broader awakening of environmental activism in the 1960s and 1970s.

There were several environmental laws passed in the early 1900s, such as the Antiquities Act and the various laws creating National Parks and National Monuments and theNational Forests. But things really took off in the 1970s with public demonstrations, protests and a variety of legislation such as the National Environmental Policy Act, Clean Water Act, Endangered Species Act, and others.

Many Environmental Historians attribute the increased attention to a few completely independent events. First, the publication of Silent Spring by Rachel Carson in 1962 is thought to have been very influential. Then there were some very well publicized environmental catastrophes in 1969 like the Cuyahoga River catching on fire and the Santa Barbara Channel Oil Spill. Those events and the raised awareness of the effectiveness of public activism borne out of the anti war movement are often cited as contributing factors. See Beauty, Health and Permanence: Environmental Politics in the United States, Samuel P. Hays, 1989. And American Environmental History, Joseph M. Pertulla, 1988 Edit: added a reference.

In the US context, many will argue that the post-war environmental movement was very much a product of its time. While it is often traced to 19th century shifts in aesthetics toward the pastoral or wilderness ideal (think Longfellow, Thoreau, Bierstadt, and Muir) there is a significant disconnect between the traditional wilderness preservation agenda (Muir again, Stephen Mather, Aldo Leopold, Robert Marshall, Howard Zahnniser, David Brower, etc.) and the "quality of life" concerns of the post-war movement whose concerns centered on water quality, air pollution, toxics, and food safety in urban areas. The former was largely male and elite-led, the later significantly more female and middle/working class as a movement. Adam Rome argues (as noted here already) that suburbanization was a major factor; the Rachel Carson acolytes will suggest it was a response to the chemical revolution of the 1930s and the toxins that give rise ro; still others will claim that it was due significantly to the basic ability of a growing middle class in the 1950s-1960s to care about these things rather than simply struggling to get by.

Benjamin Kline's First Along the River: A Brief History of the U.S. Environmental Movement (2011, 4th ed.) is a good place to start for anyone who is new to these questions and wants a basic overview. The bottom line for me is that the US story of the roots of "environmentalism" is a complex puzzle that historians are still working out. Rod Nash's classic Wilderness in the American Mind is still useful in thinking about the intellectual context <1970s, but there's been so much work done since by people like Adam Rome, Joel Tarr, Carolyn Merchant, Ted Steinberg, Karl Jacoby, Anna Bramwell, Mark Fiege, Richard White, and many more younger scholars in recent years that it's clearly still a very rich area of inquiry.

I'd like to answer your question on why it took so long for environmentalism to become a real political force by saying that it was not a political force until about 30 years later.

The environmental movement is such an interesting topic because it has grown out of a many and often competing set of beliefs. It traces its ideological roots not only to Thoreau and Emerson's transcendentalism but also Marxism, countercultural physiocracy, and Sierra Club conservationism. All these different ideas meant that when the movement began to gain traction, different ideas competed to be at the ideological core of the movement and subsequently green parties like The BC Green Party. As for why it started to grow in the 60s, it would be important to understand that the G.I. Bill had a large impact on the movement. As students stayed in school for as long as possible in order to avoid going to Vietnam, a hyper intellectual class was born that would guide the movement from the 70s onward. People had very different ideas about how to change the environment for the better and it was only until around the 1990s that the ways in which the environmentalists should enact politically was articulated. Before the 90s, the environmental movement was primarily counter culturalists who protested things like logging old growth forests, setting up communes, and creating vanguard parties. It was incredibly disjointed and I think its important to note that while the 60s lead to more people being consciousness about the harm that they could do to the environment, a “political force,” it was not.

The movement, in the 90s, split itself into about 3 different ways of explaining environmental catastrophe and what to do about it:

Deep Ecology- Deep ecologists believed that the day humans chose to see themselves as different from other animals, they were doomed. Dave foreman was the head of deep ecology and founder of Earth First! and The Monkey Wrench Gang. Dave Foreman believed that we must act like animals or face extinction. Green ecologists tended to see climate change in terms of the the gaia hypothesis. This imagined humans as parasites on the earth and as human beings caused climate change there would be, obviously, results that harmed humans. This would essentially be a way for the earth to balance out the population, killing many people, and allowing the world to be self-sustaining itself again. For example, Foreman denied sending food to Ethiopians during a famine because he believed that it was just the earth balancing itself.

Social Ecology- Social ecologists, primarily through Murray Bookchin, saw everything as social construction. Bookchin argued that the fall of humanity had begun when humans ordered themselves into hierarchies. Social ecologists believed that all of our environmental problems were related to uneven power structures and that the only way to save the environment was being more democratic in our decision making. Bookchin’s view was that the hierarchical natural of primates was not natural and should be abolished. They believed that we need to increase scale of human industrial capacity in order for everyone to be as smart as Murray Bookchin, thus realizing the drawbacks to hierarchy and liberating ourselves from environmental harm.

Ecofeminism- The book called Beyond Power by Marilyn French was rediscovered in early 90s by people who would find Bookchin appealing but also found the way he theorized the world to be disconnect from how things really work. French offers an alternative to bookchin but it is not until Riane Eisler publishes a book called the Chalice and the Blade that a movement that could be described as “ecofeminism” is born. Essentially, people fuse Eisler and French to create ecofeminism. They argued that societies based on equal partnership between sexes are much more sustainable while societies based on men are expansionist and extend too far beyond themselves.

Telling you all of that is a very roundabout way of saying that the environmental movement did not really have political force until the 1990s and even then, it was not a coherent movement with focused goals. When the first journal publish findings on climate change in 1986, some environmental movements did not even embrace it as something to be concerned about and continued to focus on old growth forests like they did in the War in the Woods. (I'm very sorry if this was not the answer you were looking for but I think its important to understand that, to this very day, the environmental movement is all over the place. I think the other historians did a good job of filling you in on pre-1960 environmentalism but it is critical to note that environmentalism was not what it is today until well until the early 2000s)

Sources:

Unfortunately much of the information I used was from lectures from Dr. Stuart Parker, former head of BC green party and professor at UBC however the following book is VERY good:

Defending the Earth: A Dialogue Between Murray Bookchin and Dave Foreman by Murray Bookchin, Dave Foreman, and edited by Steve Chase.

Also check out the following article: "Building a Green Dam: Environmental Modernism and the Canadian-American Libby Dam Project" by Philip Van Huizen