In 1877, the Italian astronomer Giovanni Schiaparelli reported seeing linear features on Mars that he called "canali" - channels. The word was mistranslated into English as "canals," implying artificial construction. Percival Lowell, scion of one of Boston's wealthiest families, seized on the idea with the fervor of a true believer. In the winter of 1893, he resolved to use his fortune to build an observatory dedicated to studying Mars.

Lowell dispatched astronomer Andrew E. Douglas to scout locations across the American West. They settled on a hill just west of downtown Flagstaff - later named Mars Hill - for its high elevation, dark skies, and proximity to the railroad. The Clark Refracting Telescope was assembled in Boston by Alvan Clark & Sons, then shipped by train to Arizona. By 1896, the observatory was operational, its founder peering through the eyepiece night after night, sketching what he believed were irrigation networks built by a dying Martian civilization. He was wrong about Mars, but the observatory he built would prove right about far more consequential things.

Clyde Tombaugh was a 24-year-old Kansas farm boy without a college degree when Lowell Observatory hired him in 1929. His task was grueling: photograph the night sky in pairs, then compare the images using a blink comparator, looking for anything that shifted position against the fixed stars. On February 18, 1930, Tombaugh found it - a tiny dot that moved between plates taken on January 23 and January 29. After weeks of verification, the observatory announced the discovery of Pluto on March 13, 1930, Percival Lowell's birthday.

The Pluto Discovery Telescope still sits on Mars Hill, a modest instrument that accomplished something extraordinary. Visitors today can peer through it and see roughly what Tombaugh saw - a sky so dark that the Milky Way casts shadows. The telescope, along with the original Clark Refractor, draws 85,000 visitors annually to a campus that functions as both active research facility and living museum.

Pluto was Lowell's headline act, but the observatory's most profound contribution to science came earlier and with less fanfare. Between 1912 and 1914, astronomer Vesto Melvin Slipher measured the spectra of spiral nebulae - what we now know as galaxies - and found that most were redshifted, racing away from us at enormous velocities. His observations provided the first hard evidence that the universe is expanding.

Slipher's work became the foundation on which Edwin Hubble built his famous law relating a galaxy's distance to its recession speed. The discovery reshaped cosmology, leading ultimately to the Big Bang theory. Lowell Observatory continued to accumulate discoveries: the co-discovery of the rings of Uranus in 1977, the detection of Pluto's atmosphere, accurate orbits for Pluto's moons Nix and Hydra, and evidence of water vapor in the atmosphere of an exoplanet. Each finding extended the reach of a hilltop observatory that started with a rich man's fantasy about Martian canals.

The Lowell Discovery Telescope, perched at 7,740 feet southeast of Flagstaff near Happy Jack, Arizona, is the fifth-largest telescope in the contiguous United States. Its 4.3-meter primary mirror weighs 6,700 pounds yet is only a few inches thick - a precisely figured meniscus held in shape by a 156-element active optics system. A unique instrument cube lets astronomers switch between five different instruments in about a minute, making it ideal for chasing fast-changing targets like gamma ray bursts and supernovae.

The telescope cost $53 million to build, with $16 million donated by Discovery Channel founder John Hendricks and his wife Maureen. Groundbreaking came in 2005, and the first image was captured in 2011. Partners including Boston University, Yale University, the University of Maryland, the University of Toledo, and Northern Arizona University share access to what remains one of the most versatile instruments in American astronomy. The telescope's naming rights went to Discovery in exchange for their gifts - not as a purchase, but as recognition. No commercial entity directs the science done with it.

Flagstaff became the world's first International Dark Sky City in 2001, and Lowell Observatory is a major reason why. The city has maintained strict lighting ordinances since 1958, ensuring that the view from Mars Hill remains one of the darkest urban skies in America. Walk the campus paths at night and the dome of the Clark Refractor glows faintly against a sky dense with stars - the same sky Percival Lowell squinted at more than a century ago, still largely unspoiled.

The observatory was designated a National Historic Landmark in 1965 and named one of Time magazine's "World's 100 Most Important Places" in 2011. The Putnam Collection Center, opened in 2014, houses artifacts spanning the observatory's history - from photographic glass plates to antique instruments used by generations of astronomers. Mars Hill remains what Lowell envisioned it to be: a place where the sky comes closer, where the darkness is an asset, and where a clear Arizona night still holds the possibility of seeing something no one has ever seen before.