Historical Timeline

Signature events from our past.

Lowell Observatory has been in operation for more than 125 years. Our history is punctuated by many important discoveries and other milestones.

Here are some of the biggest, including important scientific discoveries, recognition events, construction milestones, and other organizational milestones.


1894 - 1965

1894 Observatory Founded

Percival Lowell opened his observatory in Flagstaff, Arizona, initially to search for life on Mars.

1896 Clark Refractor Built

Percival Lowell hired the eminent telescope makers, Alvan Clark & Sons, to build a spectacular 24-inch refractor.

1912 Expanding Universe

Astronomer V.M. Slipher first detected the expanding universe after painstakingly imaging spectra of what we know today as galaxies.

1916 Percival Lowell Dies

Observatory founder Percival Lowell died at the age of 61. He is entombed in a mausoleum near his beloved 24-inch Clark Refractor.

1916 Rotunda Built

The Rotunda forms the central portion of the Slipher Building and originally housed the observatory’s library. It now serves as a museum.

Learn More

1928-’29 13-inch Telescope Built

Officially named the Lawrence Lowell Telescope, most people know this as the “Pluto Discovery Telescope”.

1930 Pluto Discovered

Clyde Tombaugh, who taught himself astronomy while growing up on a farm, discovered Pluto using the 13-inch Lawrence Lowell Telescope.

History of Pluto

1958 Lighting Ordinance

At the urging of Lowell Observatory scientists, Flagstaff enacted the world’s first lighting ordinance to protect dark skies.

Bill Cannell (left) and Patricia Bridges sketching the Moon at the Clark Refractor

1961 Lunar Mapping

Starting in 1961, cartographers worked with scientists to create maps of the Moon in support of the Apollo Moon Program.

Our Lunar Legacy

1965 Historic Landmark

The National Park Service declared Lowell Observatory a National Historic Landmark in recognition of its scientific and cultural heritage.

1977 - 2019

Rings of Uranus

1977 Rings of Uranus

A team of astronomers, including several from Lowell, used airborne and ground-based telescopes to discover a ring system around Uranus.

1988 Pluto’s Atmosphere

New Horizons image of Pluto's atmosphere

Astronomers from Lowell and elsewhere used airborne and ground-based telescopes to discover Pluto’s atmosphere.

Steele Visitor Center at Lowell Observatory

1994 Steele Visitor Center

In celebration of its centennial, Lowell opened the Steele Visitor Center in 1994.

1999 Save America’s Treasures

First Lady of the United States Hillary Clinton visited Lowell and identified

First Lady Hillary Clinton at Lowell Observatory's Clark Refractor in 1999

it for inclusion in her Save America’s Treasures program.

2012 Lowell Discovery Telescope

The 4.3-meter Lowell Discovery Telescope saw first light on April 3, 2012.

Discover the LDT

Lowell Observatory's Putnam Collection Center

2014 Putnam Collection Center

In 2014, Lowell opened the Putnam Collection Center to house its library and collection of artifacts and documents.

2019 GODO Opens

Lowell opened the Giovale Open Deck Observatory on October 5, 2019. The public facility features a roll-off building housing six telescopes.

Discover the GODO

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