Final Answer:
John Muir's concern for the wilderness around Yosemite Valley in the late 1880s led him to advocate for its protection in the late summer of 1890. His efforts culminated in the creation of Yosemite National Park in October 1890, making it the third national park in the United States after Yellowstone, established in 1872.
Step-by-step explanation:
In the late 1880s, John Muir observed the detrimental impact of grazing livestock on the natural beauty of Yosemite Valley in California. Recognizing the need for preservation, he took action in the late summer of 1890 by writing compelling articles that urged people to protect Yosemite from further degradation. Muir's dedication and advocacy efforts bore fruit when, in October of the same year, Congress officially established Yosemite National Park as the country's third national park. This development underscored the significance of Muir's work in raising awareness and mobilizing support for the preservation of natural wonders.
The creation of Yosemite National Park in 1890 marked a pivotal moment in the history of conservation and environmental protection in the United States. Muir's successful campaign not only highlighted the importance of individual efforts in safeguarding natural treasures but also demonstrated the power of public awareness and legislative action. The establishment of Yosemite National Park, following in the footsteps of Yellowstone, set a precedent for the preservation of America's pristine landscapes and laid the foundation for the national park system as we know it today.