Photo by Ben Slowey
Yerkes Observatory exterior
Yerkes Observatory in Williams Bay, Wisconsin (2026)
Celebrated as “the birthplace of modern astrophysics,” Yerkes Observatory (373 W. Geneva St.) in Williams Bay is credited for over a century’s worth of scientific breakthroughs in the field of astronomy. In addition to its storied legacy with astrophotography, revolutionizing the mapping and classifying of stars, conceptualizing the vastness of the universe and launching the first graduate PhD program for astrophysics, Yerkes is home to the world’s largest refracting telescope, the “Great Refractor,” still in good working condition after 130 years. The observatory today champions disciplinary juxtaposition with its incorporation of new arts, science and outreach programs since long-term restoration began in 2020.
Founded in 1897 by George Ellery Hale and named after Chicago finance mogul Charles Yerkes, the observatory has housed the research of legendary astronomers such as Edwin Hubble, Albert Michelson, Otto Struve, Subrahmanyan Chandrasekhar, Nancy Grace Roman, Carl Sagan and Gerald Kuiper. It is notably where the structure of the Milky Way Galaxy was first determined. “That’s probably our single most important discovery in this building,” director of programs Walt Chadick says. In the early days, astronomers and professors working at Yerkes often lived in the homes lining the observatory driveway.
Look to the Sky
Operated by the University of Chicago from its founding up until 2018, the observatory was built in Williams Bay because observatories require dark skies, and the remote area was removed from the smoke and smog of Industrial Revolution-era Chicago while still in proximity to Lake Geneva where many wealthy Chicagoans owned property. As a registered Olmsted site, Yerkes’ architecture is just as astounding as the research it houses. Famed architect Henry Ives Cobb Jr. cleverly implemented astronomy’s most common pose of looking up into his design of the building’s trompe-l’oeil rotunda, which is adorned with beads, buttresses, pointed archways and columns that altogether direct one’s eyes up to the skylight.
That said, Yerkes’ design is functional as well as aesthetically rich. The building is in a Roman cross shape where domes at either end of the “cross” house smaller telescopes while a large dome at the bottom has the Great Refractor. “It made it very easy to get back and forth between the domes when you have all this flow space,” Chadick asserts. While the original telescopes of the smaller two domes are no longer in use, the domes presently house 24-inch and 40-inch reflecting telescopes installed by the University of Chicago in the 1960s. Shortly after the observatory’s construction, cameras quickly became affixed to the telescopes with the basement containing the darkrooms while libraries and laboratories still in use today are accessible from the main hall.
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The Great Refractor is roughly 64 feet long, weighs six tons and is equipped with 40-inch lenses. Getting up to the analog telescope from ground level reveals yet another of Yerkes’ architectural marvels with its 74,000-pound elevating floor—recognized as the world’s largest indoor elevator. Looking to the ceiling, the dome spins 360 degrees. “When we rotate it, we hear people gasp on a daily basis,” Chadick attests. “This isn’t just an antique. It all works and is still used. If it breaks, we have to fix it.” He finds that viewing celestial bodies through the telescope can quickly become an emotional experience. “I’ve cried over looking at Jupiter and even the moon one time. It’s the creation of existential context for your own life.”
Astro History
Photo by Ben Slowey
Moon hypersphere - Yerkes Observatory
A hypersphere of the Moon at Yerkes Observatory (2026)
In terms of astrophotography, Yerkes vaults a collection of 180,000 glass plates, which are slivers of glass displaying positive and negative photographs of stars, planets, galaxies and other cosmic phenomena between 1900 and 1970. “These really put this place on the map,” Chadick notes. “This place is an architectural masterpiece, and it has the biggest telescope in the world, which made it a novelty, but the fact that it was taking pictures is what made it significant because people on Earth were seeing pictures from beyond the Moon for the first time. We take that for granted now.”
When it first shared its images of space with the public, the observatory sometimes received angry letters from folks accusing astrophotography of being the devil’s work. “We were just showing pictures of the neighborhood,” Chadick jokes. “Sorry!”
Dr. Amanda Bauer is head of science and education at Yerkes. Her first task upon arriving at Yerkes from Vera C. Rubin Observatory in 2022 was to ascertain whether the mounted telescopes still worked, then reactivate them along with the glass plates collection. She also devised what the research portfolio and educational programs would look like, with one of her current initiatives being to train the next generation of astronomers with hands-on access to Yerkes’ technology. “That’s not very typical of telescopes around the world these days,” she points out. “It’s a treasure trove of discovery that we now have the digital tools to access. We can get to the heart of these serendipitous observations and pull out from them the science and understanding of our universe.”
Careful Calculations
Photo by Ben Slowey
Great Refractor telescope - Yerkes Observatory
The Great Refractor telescope at Yerkes Observatory which was built in 1897 (2026).
Though astrophotography nowadays comes in the form of fully colored Hubble images, it took decades to achieve that level of detail and resolution. Bauer puts into perspective the sheer amount of steps that went into producing the images from Yerkes’ glass plates. “You would’ve had to calculate the position of an object at whatever time you were going to observe it, then get it aligned and put pieces of light-sensitive glass in line with the telescope to track an object. If you weren’t exactly lined up, then you would’ve gotten double images so there’s skill just in capturing that. Then you have to take that plate to a darkroom and spend hours on the development process with chemicals, then analyze it. What we can now do in a matter of seconds was an entire process every single time.”
The mix of analog and digital technology enables Yerkes astronomers to maximize on research obtained from the historic glass plates in a modern context. In fact, the observatory hosts undergraduate research students each summer who get trained on the telescopes and browse the glass plates to find images of certain objects through different eras. Those images then get digitized and analyzed with state-of-the-art software to determine whether the brightness or positionality of said object has changed.
Ongoing research at Yerkes involves instrumentation development led by project scientist Luke Schmidt, who is building spectrographs that measure the light properties of celestial objects. “Every object has a unique footprint, so you can learn what it’s made of, how old it is, how fast it’s moving or what direction,” Bauer elaborates. “He’s building new innovative spectroscopic techniques that we can test with our telescopes here and use our 3D printing lab to do rapid prototyping and send out to have built at scale and used for educational purposes at schools or amateur observatories.”
Yerkes Future
Restoration projects since 2020 by the Yerkes Future Foundation have included making small rooms into bigger rooms, reconfiguring power systems, replacing interior and exterior bricks, installing a new rain runoff system and placing 83 solar panels atop the building. “We’ve still got a lot of work to do,” Chadick states, citing the dome roof and catwalks as future projects. In an effort to make Yerkes’ environmental footprint as sustainable as its astronomical research, the team has overseen extensive landscaping of the observatory grounds with four miles of trails, beehives and birdhouses, newly planted native pollinators and removal of invasive flora.
Instrumental to this new chapter at Yerkes has been its introduction of arts-meets-science programming. While public astronomy events have long taken place at Yerkes, this new mission explores the many ways in which astronomy and the arts intersect. “We were pleasantly surprised to find that astronomy overlapped with sculpture and poetry and music and photography,” Chadick recalls. “Then we stretched it out with where the science of engineering matches up with those art forms. Is landscape design art or science? It’s literally both!”
These programs involve concerts, speakers, open houses, birding events, candlelight walks and hands-on workshops. Yerkes’ 2026 speaker series kicks off this Thursday, June 4 with former Poet Laureate of Wisconsin Nicholas Gulig, who is the subject of a new documentary called Welcome Poets. Other speakers this year are Sweetgrass author Robin Wall Kimmerer, theoretical physicist and writer Professor Chanda Prescod-Weinstein, arborist and writer Jeff Epping, expert mycologist Dr. Anne Pringle and Olmsted Network president Sue Bretkopf.
Chicago-based Exploding Star Orchestra, who write site-specific music and will be living on-site at Yerkes for a week, perform in the big dome on Friday, October 2 and Saturday, October 3. “I’m constantly adding programs,” Chadick assures. “Working with scientists and artists is very challenging because it’s two different parts of the brain and I’ve got to navigate both. I’m deep in the middle of that peculiar river where an astronomer and a poet are paddling in the same canoe and trying to figure out which tributary to take.”
Regional Tourist Attraction
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Glass plates - Yerkes Observatory
Astronomical glass plates, captured between 1900 and 1970, on display at Yerkes Observatory (2026)
Largely thanks to Wisconsin Secretary of Tourism Stephanie Klett, Yerkes has grown its reputation as a regional tourist attraction in recent years. Public tours of the observatory include the classic Space & Spaces tour, behind-the-scenes Hidden Spaces tour and youth-focused Kids Need Space tour. There are also ticketed night tours three days a week where folks have the opportunity to look through the Great Refractor. “If you come into an astronomy observatory and expect A, B and C, we’re trying to give you M, N and O,” Chadick laughs.
Besides the ticketed tours, a constant stream of K-12 field trips come through the observatory’s doors. Outreach astronomer Mallory Conlon recently calculated that Yerkes has welcomed more than 4,000 students since 2023. “It’s been amazing seeing groups of students come in here because you get to share this piece of history,” she affirms. “The observatory was so inaccessible for so much of its existence and now we get to change that.”
Conlon observes that the Moon hypersphere, housed in a room adjacent to the main hallway, attracts particular curiosity with children. “That visual connection to something that you see in the sky throughout your life to the history of astronomy research that happened in this building is really profound for a lot of students.” She frequently gets questions about exoplanets as well, which for many kids opens the door to deeper conversations about whether aliens exist.
“I really find art to be a way to process scientific ideas, especially for younger students,” Conlon shares. “It can provide concrete and tangible callbacks for when they’re remembering a scientific concept. For example, an activity I love to do with our school groups is tell them about a moon that orbits around Jupiter called Europa, which has an icy crust and is really frigid and cold. Scientists believe that under kilometers of ice that there is a saltwater ocean likely heated by hydrothermal venting. I have students design an alien that could live on Europa, so not only are they processing the different properties of that moon and how it connects to life here on Earth, but they’re also thinking about what sort of traits would life need to thrive in an environment like this.”
Dark Sky Advocacy
The observatory also engages in dark skies advocacy, encouraging communities to reduce light pollution whenever possible for environmental and ecological reasons. “It is a topic that culminates in what Yerkes is all about, which is the idea that humans can advocate for change that impacts many different aspects of life from astronomical research to caring about your environment,” Conlon reckons. “There’s also cultural considerations, where we lose a huge part of our heritage as humans when we lose the night sky. Stars were a means of not just storytelling but finding your way through this universe.”
This summer, Yerkes is partnering with artist and musician Noelia Cruz on A Shell in the Sky, a curated exhibition of Indigenous artists sharing Anishinaabe art, star knowledge and cultural wisdom within the observatory. The opening ceremony is this Saturday, June 6 at 6 p.m. with the exhibit on display through October. “There’s a deep history of studying and learning about the sky and how that knowledge is still being carried on today by Indigenous groups of the Midwest,” Conlon acknowledges. “We’re super excited about this idea coming to fruition and it will be a really special experience.”
Off-campus Astronomy On Tap events hosted by Yerkes take place throughout the year at Deusterbeck’s Brewery Company (N5543 County Rd O) in nearby Elkhorn. Conlon contends, “There’s a lot of opportunities to be creative here with really special programming that truly can’t happen anywhere else.”
Visit the Yerkes Observatory website to learn more or support its work. Purchase upcoming event tickets here.
