Into the 60s and 70s
Throughout the 1940s and 1950s the Save-The-Redwoods League continued its efforts to conserve as much as the ancient redwood forests of California as possible. However, with the U.S.'s involvement in World War II and then the Cold War, the League was unable to accomplish much. By the early 1960s though the movement for the protection of the redwoods had been renewed and was bigger than ever.
In 1961, the Save-The-Redwoods League joined forces with the long established Sierra Club, and the National Geographic Society to revive the idea for a Redwood National Park.  The movement for a Redwood National Park was not limited to Humboldt County, nor to the State of California. The creation of a Redwood National Park was a global movement with supporters all over the United States, Europe, and even China.
The movement for the creation of a Redwood National Park came to a head in 1967 when a bill that would establish a Redwood National Park was presented to the United States Congress. In April of 1967, the Subcommittee on Parks and Recreation of the Committee on Interior and Insular Affairs held hearings to discuss the creation of a Redwood National Park. The hearings were open to the public and several individuals and organizations spoke in front of the committee.
Among those who spoke in favor of the national park was Ralph W. Chaney, president of the Save-The-Redwoods League. He addressed the subcommittee in a brief statement recapping previous statements the subcommittee had heard simply adding:
"I want to add only one point, and speak in terms of one hundred million, not a hundred million dollars, but a hundred million years, for that is the time that trees like our coast redwoods have lived in North America and widely over the other parts of the world. It is the heritage of 100 million years brought down to the narrow coast belt of California and adjacent area." 
During this period, when the U.S. Congress was debating the creation of a Redwood National Park, the Save-The-Redwoods League wasn’t the only one making the argument that the redwoods on the northern California coast needed to be protected because they were among the oldest and tallest living things on earth. Several newspapers and journals covering the story made the same point.
"...if Congress does not act promptly, they [the lumber companies] can be expected to resume their cutting. Some of the finest redwood stats left, including the world's tallest trees, lie in the path of their saws."
-“Last Chance to Save the Redwoods?” Courier-Journal, 2 February 1967
"These redwoods are the tallest trees in the world. No words or pictures can do them justice- they must be seen for a full appreciation of their magnificence. Soon only the redwoods in protected park areas will be left, for the rest will have fallen to the ravages of lumbering."
-“Redwood Park: Let’s Think Big” Erie, PA, Times-News, 17 January 1967
"It is an empire the like of which exists nowhere else on earth, for its imperious inhabitants are Sequoia sempervirens, among the tallest trees in the world and among the oldest of living things… Many of the trees that were sprouting their leaves when Hannibal crossed the Alps now serve as durable shingles and siding, patio tables, and other amenities of our ephemeral culture."
-“Life and Death of a Primeval Empire” American Heritage February 1967
The Movement was successful, and on October 2nd 1968 a bill was signed that created a Redwood National Park protecting over 100,000 acres of coastal redwood forests. Another bill was passed by Congress in 1978 adding an additional 48,000 acres to the park.
 Save the Redwoods League, http://www.savetheredwoods.org/about-us/mission-history/league-milestones/
 U.S. Congress Senate, Subcommittee on Parks and Recreation of the Committee on Interior and Insular Affairs. Redwood National Park: Hearings before the Subcommittee on Parks and Recreation of the Committee on Interior and Insular Affairs. 19th Cong., 1st sess., April 17 to April 19, 1967