Task: Question Generation
Input (English): Passage: The Three Sisters area was occupied by Amerindians since the end of the last glaciation, mainly the Northern Paiute to the east and Molala to the west. They harvested berries, made baskets, hunted, and made obsidian arrowheads and spears. Traces of rock art can be seen at Devils Hill, south of South Sister.
The first Westerner to discover the Three Sisters was the explorer Peter Skene Ogden of the Hudson Bay Company in 1825. He describes "a number of high mountains" south of Mount Hood. Ten months later in 1826, the botanist David Douglas reported snow-covered peaks visible from the Willamette Valley. As the Willamette Valley was gradually colonized in the 1840s, Euro-Americans approached the summits from the west and probably named them individually at that time. Explorers, such as Nathaniel Jarvis Wyeth in 1839 and John Frémont in 1843, used the Three Sisters as a landmark from the east. The area was further explored by John Strong Newberry in 1855 as part of the Pacific Railroad Surveys.In 1862, to connect the Willamette Valley to the ranches of Central Oregon and the gold mines of eastern Oregon and Idaho, Felix and Marion Scott traced a route over Scott Pass. This route was known as the Scott Trail, but was superseded in the early 20th century by the McKenzie Pass Road further north. Around 1866, there were reports that one of the Three Sisters emitted some fire and smoke.In the late 19th century, there was extensive wool production in eastern Oregon. Shepherds led their herds of 1,500 to 2,500 sheep to the Three Sisters. They arrived in eastern foothills near Whychus Creek by May or June, and then climbed to higher pastures in August and September. By the 1890s, the area was getting overgrazed. Despite regulatory measures, sheep grazing peaked in 1910 before being banned in the 1930s at North and Middle Sister, and in 1940 at South Sister.In 1892, President Grover Cleveland decided to create the Cascades Forest Reserve, based on the authority of the Forest Reserve Act of 1891. Cascades Reserve was a strip of land from 20 to 60 miles (30 to 100 km) wide around the main crest of the Cascade Range, stretching from the Columbia River almost to the border with California. In 1905, administration of the Reserve was moved from the General Land Office to the United States Forest Service. The Reserve was renamed the Cascade National Forest in 1907. In 1908, the forest was split: the eastern half became the Deschutes National Forest, while the western half merged in 1934 to form the Willamette National Forest.
Output (English): What is the full name of the forest that was split in 1908, with the eastern half becoming the Deschutes National Forest, and the western half merging in 1934 to form the Willamette National Forest?