Earliest evidence of human inhabitants of the Glen. The skeletons of two people were discovered in a deposit of calcium carbonate near Grinnell Mill in 1924. Researchers determined that these were Paleo-Indians who had drowned in a bog.

The mound-building Hopewell visit the area around the yellow spring. A mound they left behind, first excavated in 1953, contained the remains of an adolescent male. Later digs produced other skeletons and stone artifacts including a spear point and sharpening

People of the Hopewell culture construct an earthwork enclosing about 6 acres in the South Glen, plus two small earthen mounds. The enclosure was named the “Bell Works” after the 1850s landowner Dr. William Bell. A map and description of the site was included in Ancient Monuments of the Mississippi Valley, published by the Smithsonian in 1848. The earthwork, studied by Wright State archaeologists in 1986-7, is believed to have been a ceremonial site used by local Hopewell families.

Miami Indians use the Yellow Spring as a watering point on the route to Old Piqua, an important trading center on the Mad River near Springfield.

At the conclusion of the French and Indian War, the Miamis, who sided with the losers, are driven out of Ohio by the Shawnee, allies of the British. An important Shawnee settlement just south of Glen Helen called Chillicothe (now Oldtown) becomes a central point in local pioneer history as the birthplace (or thereabouts) of Chief Tecumseh, as the site of the gauntlet run by frontiersman Simon Kenton, and as the place where the Shawnee adopted Daniel Boone.

Lewis Davis purchases the land around the Yellow Spring from John Cleve Symmes, who owns a quarter million acres in Southwest Ohio. Davis, Yellow Springs’ first white settler, builds a tavern at the spring and begins advertising the water’s “curative effects” in Cincinnati newspapers.

“The Bullskin Trace,” a Shawnee migration route from the Ohio River to Detroit, running right by the Yellow Spring, becomes a State Road. (The Shawnee appreciate greatly the “Golden Waters” temperature of 52 degrees Fahrenheit.)

Along the Little Miami River, construction begins on what is now known as Grinnell Mill. One of several mills that operated in Glen Helen, it is the only one that remains.

A short-lived experiment in communal living begins near the Cascades. A group of Owenites, followers of British industrialist and utopian socialist Robert Owen, attempt to live together in a great log house, but disband within two years.

Elisha Mills buys the Davis property, and starts building a hotel near the yellow spring. Encompassing a mansion house and six brick and frame cottages, the hotel offers 48 rooms “expressly for families.”

Cincinnati-based meatpacker William Neff buys the Yellow Spring property, which then becomes known as Neff Park. Though purchased as a summer home, the Neff’s continue to expand on its function as a resort.

Completion of the Little Miami Railroad results in a flourishing business in the Glen of quarrying limestone, which is then crushed and processed into lime for use in concrete and fertilizer.

The “Glen Forest Water Cure” opens in the “Sheldon Glen” an area north of Grinnell Road, but south of the Neff property. A staff of physicians employs the water to cure peoples’ “bilious affections.”

The water cure facility begins operation as the Memnonia Institute, a school of physical and spiritual harmonics under T.L. and Mary Gove Nichols. Notorious for their published writings on free love, the Nichols are soon invited to leave by an outraged delegation of local residents, including Horace Mann, Antioch College’s first president. In 1862 the structure burns to the ground.

A group of 31 escaped slaves escape to Ohio with support of their owner’s son, Moncure Conway, and build a settlement in what is now Glen Helen. The leaders of the group, Dunmore and Eliza Gwinn, stay in the area. Three generations later, a family member, Jim McKee, becomes a popular chief of police in Yellow Springs.

The sons of William Neff build a quarter-million-dollar hotel next to the original one at the Yellow Spring. Expecting immense profits from Southern vacationers, the Neff brothers construct a magnificent 246-room building that lives up to its billing but fails financially. Also in 1869, local baseball star and naturalist Hugh Taylor Birch leaves Antioch College for Chicago one course shy of graduating.

The Neff hotel closes, just 13 years after it opened. It is dismantled several years later.

Neff Grounds Park, including the lake, opens on land below the Yellow Spring. A dance pavilion is built near Route 68.

To kick off the summer term at Antioch College, newly elected college President Simeon Fess holds the first Antioch Chautauqua in the Glen. As many as 25,000 visitors in a single day flock to see famous lecturers, hear musicians, and enjoy performances of Shakespeare under a big top. Fess develops political contacts as the event’s emcee, eventually becoming a U.S. senator and chairman of the Republican National Committee.

The Ohio National Guard has its annual encampment at the Neff Park.

To prevent the sale of the Glen to developers interested in building an amusement park there, Arthur E. Morgan, the new president of Antioch College, has the land around the Yellow Spring condemned as a water source. The spring briefly supplies water to the village, and its high iron content turns everything it touches orange.

Antioch acquires its first piece of the Glen from the estate of John Bryan, an eccentric millionaire famous for his atheism and for building the largest barn in the world.

Helen Birch Bartlett dies of cancer at the age of 42.

Through Arthur Morgan’s wife Lucy, Hugh Taylor Birch is reconnected with Antioch. In the sixty years since leaving school, Birch became a very successful attorney and real estate investor. Remembering his fond memories of the Glen, Birch determines to buy it all, and donate it to the college in memory of his daughter, Helen. From this point forward, the land is renamed Glen Helen. Birch builds a large home in the South Glen as his summer residence. Also in 1929, Antioch College constructs a coal-fired power plant to supply heat to the campus, and electricity to the Village of Yellow Springs. The plant is placed within a quarry in Glen Helen, directly on top of a natural spring.

With the help of his stalwart assistant, Carmelo Ricciardi, Birch builds trails, plants trees, and clears several springs in the Glen, a practice the two continue for the next twelve years.

Birch presents a statue of Horace Mann to Antioch on the 100th anniversary of public education in America. Cast from the same mold as the original at the Massachusetts statehouse, the statue stood within the Glen on land that Mann owned while president of Antioch.

A year before his death at the age of 94, Hugh Taylor Birch donates a half-million dollars to Antioch College to start an endowment for Glen Helen.

Kenneth Hunt, a biologist and geologist from Massachusetts, becomes the first director of Glen Helen and promotes its use for outdoor education.

The first planting of Christmas trees in what later becomes the Bryan School Forest is a conservation measure designed to promote community relations between Antioch and Yellow Springs and to control the harvesting of pines in the Glen each Christmas. The effort is the first example of an educational forest in Ohio.

The Yellow Spring is redesigned in its present form by local landscape architect Louise Odiorne.

Trailside Museum is dedicated, along with the Inman steps, named for Professor of Biology Ondess Inman, both built from the ruins of kilns left over from the lime industry.

The Outdoor Education Center opens, its facilities built of lumber recycled from a recreation pavilion in the Glen and from WWII-surplus barracks used by the college to house veteran students in the postwar era. The center, the first such facility in the Midwest, quickly becomes a model for residential “school camps” that follow.

The Ohio Department of Transportation proposes a bypass through the Glen for Route 68. Swift, broad-based public outcry results in the plan’s abandonment within the year.

Village Council begins planning a sewer to run across the Glen, another effort that is met with stiff opposition. Through private donations and a compromise in which some Glen land is ceded to the Village, the sewer is rerouted. Also in 1959, the Riding Centre is established when Antioch Professor Louise Soelberg leases 15 acres of the Glen to start a horse riding program

As a direct result of recent threats to the Glen, the Glen Helen Association forms to further protect the Glen from encroachment.

A proposal by the federal Soil Conservation Service to build a flood-control dam in the South Glen is abandoned, due in part to strong opposition from the college, the Village of Yellow Springs, and other local interests.

In a tragic act of arson, the Jacoby Road covered bridge is destroyed by fire. The bridge, which spanned the Little Miami and marked the south end of Glen Helen, had been the longest covered span in Greene County.

The Raptor Center opens, the brainchild of Glen Helen naturalist Steve Kress. Dr. Kress later goes on to ornithological fame for his work reintroducing the Atlantic puffin and other seabird species to the United States.

Ken Hunt retires after nearly 30 years of service. Ralph Ramey, a wildlife conservationist and administrator in the Metropolitan Park District of Columbus, Ohio, becomes Director of Glen

The Vernet Ecological Center, opens, a gift from the foundation endowed by Sergius Vernet. This one of a kind structure was the result of an artistic rendering by Read Viemeister, architectural specifications from Jack Klein, and construction by Bill Hooper. It features three rounded sections, joined by short hallways, and clad in local limestone and southern yellow pine, a facade designed to mirror the surrounding landscape.

A covered bridge destined to be destroyed by the creation of Caesar’s Creek Reservoir in New Burlington is transported to the Glen. Originally intended to replace the Jacoby Road span, the bridge is shortened and placed over the Yellow Springs Creek after it was found that only the middle third of the long bridge was structurally sound.

Restoration begins on Grinnell Mill, under the supervision of Jim Hammond. The structure, now approximately 200 years old, is one of the last remaining mills on the Little Miami River and is listed in the National Register of Historic Places.

In partnership with the Tecumseh Land Trust and the Trust for Public Land, the final in a series of modern conservation easements are placed on the entirety of Glen Helen. The easements are designed to ensure that the land will forever be protected from development. Also in 2015, Glen Helen acquires Camp Greene from the Girl Scouts of Western Ohio. The camp features a 1920s lodge set on an overlook above the Little Miami River.

In March, as the coronavirus pandemic moved into Ohio, public access to Glen Helen was closed. Most staff were furloughed. The Outdoor Education Center suspended its programs and sent the naturalists home, with no plans to reopen. Into the fray, the Glen Helen Association stepped forward with the commitment to purchase and reopen the preserve. The purchase agreement becomes official in September, and the preserve is promptly reopened to the public.

A family of beavers begins a dam on the main stem of the Yellow Springs Creek. The resulting pond, over an acre in size, dramatically changes the habitats of the Yellow Springs Creek valley. The Horace Mann monument is removed from Glen Helen and relocated to the Antioch College campus.

As a component of its Campaign to Secure the Future of Glen Helen, the derelict Antioch College Power Plant is torn down. A wetland immediately begins to form on the site of the former structure.