The Lowell Observatory, Flagstaff AZ 

Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965.
What is Lowell Observatory famous for?
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Lowell Observatory is known for its legacy of cutting-edge research ranging from detection of the first evidence of the expanding universe in 1912 and discovery of Pluto in 1930, to modern-day studies of the solar system and beyond with one of the world's most powerful tools for exploring space, the Lowell Discovery ...