Octagon Open Houses | April 14th and 15th, 2024

The Octagon State Memorial, Newark Earthworks Map.
Image courtesy of the Ancient Ohio Trail.

The Octagon State Memorial is one of the most spectacular surviving remnants of the Newark Earthworks and is part of the Hopewell Ceremonial Earthworks.

The Octagon is connected to a perfectly circular enclosure 1,054 feet in diameter. The architecture of the Octagon Earthworks encodes a sophisticated understanding of geometry and astronomy. It is a National Historical Landmark and part of the Hopewell Ceremonial Earthworks UNESCO World Heritage site.

The precise geometry of Newark’s circle-octagon centers on its axial center line, beginning at the center of the Observatory Mound and pointing 38 degrees north of east. It’s a long line of sight which, if the site were cleared of trees, would lead the eye to a precise point on distant horizon. From here, as a result of generations of careful measurements and designing, the American Indians 2,000 years ago could predict, and bear witness to, the return of the moon to its northernmost position – just once every 6,789 days.

The movements of the moon are complex. Nowadays, we notice that the moon has different phases over about 29 days. But the builders of the earthworks noticed much more complicated lunar patterns: first, about every four weeks its rising point swings back and forth between the southeast and the northeast; and second, the width of this angle expands very slowly over about 9 1/3 years (about 3395 days), and then contracts again at the same rate. The moon’s setting points move the same way across the western horizon.

So there are eight points where the moon appears to reverse direction along the horizon during this long, complex cycle. Remarkably, all eight are marked precisely by these earthen walls and gateways. The architecture here tells us which one mattered the most: the extreme northernmost moonrise perfectly aligns along the central axis of the Octagon. This happened only once in 18.6 years or 6,789 days.

Portions of the Octagon Earthworks is open to the public during daylight hours 365 days a year, but much of the site is used as a private golf course for most of the year, so access is restricted. Five times this year, however, golfing is suspended and the entire site is made available to the general public.

The grounds of the Octagon State Memorial [external link] will be open to the public for general strolling and viewing from sunrise to sunset.

Octagon State Memorial, 125 N. 33rd Street, Newark, OH 43055

Take your tour with you, with The Ancient Ohio Trail [external link].

We hope to see you there!

Can't make it this time? The other Open Houses this year are: 

• Monday, July 22nd
• Sunday, October 20th
• Monday, October 21st

For more information, visit Ohio History Connection [external link].