In the early 1900's, Americans were first settling in the U.S.They didn't have much knowledge but one thing they did know was how to use their natural resources to help expand their cities and build factories, houses, crops, etc.
In the process of building towns, they would destroy forests, lakes, and rivers, slowly ruining the resources they did have. Doing so enabled tremendous economic growth, but it also came at a cost to the environment. At this rate only a fraction of the country's virgin, or original, forests were still standing.
Economic activities were also polluting the air in urban areas. Once factories were built, the smoke in the air was so bad that it made it difficult for people to breathe. The air smelled like sulfur, ammonia, kerosene, acid fumes, and phosphate fertilizer. Not only were the humans affected by this, but so were the animals.
If the community kept going at this rate they would lose their resources very quickly. People's health was at risk as long as they kept on polluting the air and streets with garbage. To help this, Roosevelt, President at the time, and John Muir, a conservationist, decided to come together and think of solutions.
The two set aside national forests so people could not tear down tress freely and waste other natural resources. As for the air pollution not much was changed. Laws were not made to fix the problem but it was brought up to the community for awareness.
In the present, there have been more attempts to fix these problems such as laws for businesses and factories and also for the community members to help keep cities clean. There are littering laws to keep the streets free of garbage. The Environmental Protection Agency that limits how much pollution is in the air. Slowly we are working together to keep our world as clean as possible.