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.