Lowell Observatory was established in 1894, which places it among the oldest observatories in the United States. It was founded by astronomer Percival Lowell of Boston's Lowell family. It was designated a National Historic Landmark in 1965.
Lowell hired astronomer Andrew E. Douglass to find a location, and they chose Flagstaff for its elevation, dark night skies and nearness to the railroad. The materials were sourced locally, but the Clark Refracting Telescope was assembled in Boston.
The 24-inch Clark Refracting Telescope was built in 1896 and is still used for public observing. Astronomers in 1963 used the observatory while the Moon was being mapped for the Apollo Program, and many astronauts looked through the Clark Telescope.