Arboretum History

Nearly a century of innovation, progress, and impact for trees

Content Detail

Joy Morton

The Morton Arboretum was founded in 1922 by Joy Morton, whose father founded Arbor Day. Over the decades, the Arboretum has continued to evolve, while staying true to the Morton family motto, “Plant Trees.”

Joy Morton (1855–1934) founded the Morton Salt Company in Chicago in 1885. It became the leading salt producer in the U.S. and Canada.

Joy was the eldest of four sons of J. Sterling Morton (1832–1902), the originator of Arbor Day. “Plant Trees” was the Morton family motto. Arbor Lodge, the family home in Nebraska City, Nebraska, is now a state park. Joy’s mother, Caroline Joy French (1834–1881), loved gardening, and Joy inherited both of his parents’ interests in trees and horticulture. (“Joy” was an ancestral surname in Caroline’s family.)

As a Chicago industrialist, Joy discovered the pastoral setting of Lisle, 25 miles west of the city, in 1909 and built his country estate there, calling it Thornhill. By 1921, the work of transforming the property into an arboretum, or an outdoor museum of trees, became a meaningful pursuit for Joy’s later years, furthering his family’s tree-planting legacy as a supplement to his business success.

In starting The Morton Arboretum, he sought the advice of Dr. Charles Sprague Sargent (1841–1927), Director of the Arnold Arboretum of Harvard University for 50 years. Sargent visited Lisle several times and became a significant influence in shaping The Morton Arboretum. He suggested important European gardens for the Mortons to visit, hired and trained key personnel, recommended landscape architect O.C. Simonds (1855–1931), promoted early establishment of an herbarium and library, donated herbarium specimens, books, and living plants, edited the statement of purpose, and offered general advice and encouragement.

The Morton Arboretum was formally established on December 14, 1922. Joy appointed seven family members and two Morton Salt executives to life terms on the Board of Trustees, ensuring long-term continuity of leadership and fulfillment of goals.

When Joy died in 1934, the Arboretum consisted of 735 acres. It had a general landscape plan, many plantings and nurseries, an extensive system of roads and paths, and a small but excellent staff. It was operated out of renovated farm buildings and the library (now designated the Founder’s Room at the Thornhill Education Center).


Four Columns

Inspiration and intrigue surround the sculptures known as the Four Columns along the Conifer Walk on the Arboretum’s East Side.

The four stately white columns providing a focal point at the end of the Hedge Collection represent the inspiration of Suzette Morton Davidson, granddaughter of Arboretum founder Joy Morton. In 1960, Suzette urged her father Sterling Morton, then Chairman of the Board, to commission architect Arthur Myhrum to build the 19-foot tall cylindrical structures, reminiscent of four handsome columns that divided the rooms in her Chicago apartment. Intrigue surrounds the meaning of the Four Columns, which have been said to signify the four seasons (winter, spring, summer, fall), the four Morton brothers (Joy, Paul, Mark, Carl), or pillars of salt (in correlation with Joy Morton’s business enterprise). The columns are hollow and have a surface aggregate of northern Michigan dolomite to ensure a lasting white color.

Morton Family Cemetery

Arboretum founder Joy Morton set aside this one-acre parcel as a family burial plot in 1925. It is the final resting place for Joy and members of his family.

The Morton Family Cemetery is situated at the base of the sloping terrain in a southeast corner behind the Thornhill Education Center, which once was the site of the Morton family home.

The original design was formal at the center and encircled by a trail through a naturalistic arrangement of oaks, yews, and hawthorns. Some of the trees that framed the space in 1925 still remain. Thanks to a generous donation by an extended family member, many improvements were made in 2006. The original iron fence around the formal section of the cemetery was refurbished, an interpretive panel was posted, and new plantings were added.

Joy Morton was the first to be interred in the family plot upon his death in 1934. Others memorialized there include granddaughters Caroline Morton (1921) and Millicent Morton (1929), wife Margaret Morton (1940), brother Mark Morton (1951), son Sterling Morton (1961), daughter-in-law Sophia Preston Morton (1969), granddaughter Suzette Morton Davidson (1996), and Suzette’s husband Eugene Davidson (2002).

Thornhill Education Center

The Thornhill Education Center has had an important role in the Morton family and in the services of The Morton Arboretum.

Located on the West Side of the Arboretum, the Thornhill Education Center is on the site of the original Morton family mansion. Constructed in 1910, the home was razed in the early 1940s following the passing of Joy Morton’s wife, Margaret, who was the last family member living there. The family’s request was to have an education center built on the site. A library, which had been added to the home in 1923, was preserved as part of the Thornhill Education Center and is now called the Founder’s Room. The Thornhill Education Center was renovated and refurbished in 1993, providing modern facilities for an expanding education program. Today space is also available for private rentals.

The landscape around the Thornhill Education Center contains a mix of plants including original specimens that surrounded the mansion during the days of Morton residence. Notable plants around Thornhill include White Tigress maple (Acer ‘White Tigress’) and Accolade™ elm (Ulmus ‘Morton’).

Founder’s Room

When the Thornhill Education Center opened in 1942, it replaced most of Joy Morton’s mansion. Only the original library, now known as the Founder’s Room, remains.

This room, with its English oak paneling, carved stone mantelpiece, and decorative plaster ceiling, looks much as it did when it served as Morton’s private library. It features exhibits of photographs, letters, and other memorabilia pertaining to the Morton family and Arboretum history. (The Sterling Morton Library, located in the Administration and Research Center, opened in 1963 and continues to serve as the Arboretum’s current library.)

Trees commemorated in stained glass

Joy Morton incorporated his passion for trees into his library. On the south wall is a bay of 10 windows containing stained-glass medallions depicting famous trees from history and legend. To see a photo of a particular stained-glass medallion, click on the title below.

Generations pass while some trees stand

The quotation encircling this image comes from the seventeenth-century sage Sir Thomas Brown who pondered mortality in his essay Hydriotaphia (1658). Find the second part of this two-part quotation on window 6.

Linnaeus linden

The seated figure is Carl Linnaeus, with two figures (possibly his parents) beside him and a linden tree above. What does a linden have to do with the father of modern plant and animal taxonomy? When Carl was born in 1707, most Swedish people had no surnames. His father coined the surname Linnaeus after a linden tree that had given their family property, Linnagård, its name.

Trysting tree of Robin Hood

The heroic thief Robin Hood, depicted here in red, regularly met with his fellow yeomen at a tree dubbed their trysting tree. In various folklore ballads and tales, the tree serves as a gathering spot, a place to hide from the Sheriff of Nottingham, and a location for Robin to meet with his love Maid Marian.

Justice tree

A reference to “1300” gives a clue to this image, which probably represents a scene from Dante Alighieri’s Divine Comedy, set in 1300. In the final cantos of Purgatorio, Dante uses a tree to represent the divine justice of God on earth. “Lime tree,” a permutation of line or linden tree, refers to the traditional role of lindens as trees of justice in mythology.

King Xerxes’ plane

According to Greek historian Herodotus, in 480 B.C. King Xerxes of Persia stopped his army in a grove of stately plane trees. Smitten by one tree’s exceptional beauty, he adorned it with jewelry and put off conquering Greece for a few days. The delay cost the Persians the war.

And old families last not three oaks

The second part of Sir Thomas Brown’s quotation (see window 1 for the first) emphasizes the briefness of human immortality. Three successive oaks, he says, live longer than our memory of even old families. “Hesperides” refers to a mythological garden with golden apples that bestow immortality.

Washington Elm, Cambridge, 1775

George Washington did take command of the American army in Cambridge, Massachusetts, in 1775. There is no official record, however, that he did so under an elm tree. Nonetheless, in the 1830s just such a legend became attached to one stately elm. The tree died in 1923, but the legend endures.

Council Magnolia, Charleston

Charleston, South Carolina, never had a “Council Magnolia.” It did, however, have a Liberty Tree, under which Charlestonians heard the Declaration of Independence read for the first time. The artist was probably thinking of that tree—with one error. The Liberty Tree was an oak, not a magnolia.

Treaty tree, Philadelphia, 1683

In 1683, William Penn and Lenape tribe leaders entered a historic peace treaty that paved the way for the founding of Philadelphia. The event possibly took place under an elm tree, or at least it did in a famous 1771 painting of the meeting. That painting’s popularity guaranteed the tree’s immortality even after it fell in 1810.

Charter Oak, Hartford, 1687

Connecticut’s celebrated tree rose to fame after King James II, hoping for more control, sent an agent with an armed force to seize the Charter of Connecticut in 1687. According to legend, colonial leaders hid the charter in a white oak tree, which soon became a symbol of liberty. It fell in 1856.

Historical Timeline


J. Sterling Morton (1832-1902), father of Arboretum founder Joy Morton (1855-1934), established Arbor Day in Nebraska. (He later served as Secretary of Agriculture under President Grover Cleveland.)


Joy Morton acquired property in Lisle, Illinois, where he built his country estate and named his home Thornhill.


The Morton Arboretum was founded in 1922 by Joy Morton with a focus on living collections, a research library, and a herbarium.


Joy Morton died. His daughter, Jean (Mrs. Joseph M. Cudahy, 1883-1953), became Chair of the Board of Trustees and served in that capacity for 19 years. Under her leadership, the Arboretum developed a national reputation. In memory of her father, she built the Administration Building, which provided a reception area for guests, staff offices, and space for the herbarium and library. The Hedge Garden was established, making it the oldest hedge demonstration in a U.S. public garden.


Mrs. Cudahy commissioned a custom-designed open air bus to provide tours of the grounds for visitors; it was inspired by vehicles used at the World’s Fair (“A Century of Progress”) in Chicago in 1933-1934.


The Ground Cover Garden was planted.


Clarence Godshalk (1897-1988) was named director. He had commenced his employment as superintendent of the grounds in 1921. Trained as a landscape architect in the naturalistic style of O.C. Simonds and others, he further developed the Arboretum’s distinctive landscapes.


Mrs. Cudahy started the Arboretum’s renowned education program by inviting the gifted naturalist and ecologist May Theilgaard Watts (1890-1975) to teach.


Thornhill Building, a new educational facility, opened on the site of the razed Morton mansion. May Watts developed an innovative public education program, the first such program among U.S. arboreta. She was also known for her Tree Finder and Flower Finder identification books, and her book Reading the Landscape (1957, revised 1975 and 1999). In 1963 she originated the Illinois Prairie Path, the first rails-to-trails project in the U.S.


A rustic Outpost with overnight accommodations was completed to house week-long workshops and later a 5th grade residential environmental education program.


Sterling Morton (1885-1961), son of Joy Morton, became Chair of the Board of Trustees after his sister Jean’s death, serving for eight years. Achievements during his tenure included adding a new research wing to the Administration building, initiating a practical research program; dedicating an auditorium in the building to Jean; increasing the size of professional staff; and adding considerable acreage.


Construction of the East-West Tollway and widening of Illinois Route 53 changed the Arboretum landscape, resulting in new lakes, roads, and a staffed gatehouse.


An admission program went into effect.


Suzette Morton Davidson (1911-1996) became Chair of the Board of Trustees after her father Sterling’s death, serving for 16 years.


The Schulenberg Prairie restoration project began.


The Sterling Morton Library was built, and Mrs. Davidson greatly expanded the rare botanical book and art collection. A formal scientific Research program was established.


After 45 years at the Arboretum, Clarence Godshalk retired and was succeeded as director by Dr. Marion Trufant Hall (1920–2020), a scientist of broad interests and experience. Over the next 24 years he led the Arboretum’s growth as a major scientific and cultural institution. An elm-breeding program was started to develop hybrids resistant to Dutch elm disease.


The Plant Clinic opened.


The Arboretum celebrated its 50th anniversary. A general master plan was developed; the Visitor Center was built in memory of Suzette’s mother; a membership program was inaugurated; the first catalog of the plant collections was published; and an exhibition of the Arboretum’s rare books was held at the Newberry Library in Chicago.


The first stand-alone Visitor Center opened.


The Arboretum was accredited as a museum by the American Association of Museums.


Suzette Morton Davidson retired and selected her successor, Charles C. Haffner III, as the first person outside the Morton family to serve as Chair of the Board of Trustees.


The volunteer program was formalized.


The new Research Center was dedicated.


The Fragrance Garden was developed.


Dr. Gerard T. Donnelly, a botanist with background in forest ecology and experience in teaching and garden administration, was hired as Executive Director and later was titled President and CEO.


W. Robert Reum was elected Chair of the Board of Trustees.


The Branching Out! strategic initiatives and first-ever capital campaign resulted in new programs, services, and facilities, along with expanded outreach to the public. Projects coming to fruition this year included a visible and welcoming entrance to the Arboretum, an environmentally-sound main parking lot, a new Visitor Center, a Maze Garden, and a restored Meadow Lake.


As part of the Branching Out! site redevelopment, the four-acre Children’s Garden opened. The Morton Arboretum co-hosted the American Association of Botanical Gardens and Arboreta annual conference in Chicago and suburbs.


The Morton Arboretum led the creation of ArbNet, a program that identifies arboreta worldwide, offers opportunities for exchanging professional information, and provides an accreditation program for them. The Morton Arboretum received accreditation as an arboretum through ArbNet.


The Morton Arboretum renewed its accreditation as a museum with the American Alliance of Museums.


The Morton Arboretum launched the Chicago Region Trees Initiative—a collaborative effort to build a healthier urban forest in the seven-county region. Also, the Arboretum introduced a major wintertime exhibition, Illumination: Tree Lights at The Morton Arboretum.


Darrell B. Jackson was elected Chair of the Board of Trustees.


A five-year project began to restore the section of the East Branch of the DuPage River that runs through the Arboretum. For the first time, the Arboretum served 1 million annual visitors.


The Growing Brilliantly campaign was publicly launched to raise support for a new curatorial and operations center, Center for Tree Science, tree conservation programs, new plant development, and Children’s Garden enhancements. The curatorial and operations center opened, as did a new education support building. Christopher B. Burke was elected Chair of the Board of Trustees.


Arboretum operations were curtailed in unprecedented ways by the coronavirus pandemic, starting March 16, causing closure of the grounds in April and May and otherwise limiting programs and services in the months to follow. However, efforts were active to maintain contact with members and the public, and offer adjusted operations, creative alternatives, and innovative solutions to keep people engaged with the tree-focused mission. Stephen C. Van Arsdell was elected Chair of the Board of Trustees.


To commemorate the Arboretum’s centennial year, and to honor the organization’s longtime President and CEO upon his retirement at the end of the month, The Gerard T. Donnelly Grand Garden opened to the public on September 18. Upon the 150th anniversary of Arbor Day in April, the Arboretum launched the Centennial Tree Planting Initiative to plant 3,000 trees throughout the Chicago region. Additionally, three new sculptures were added to the Human+Nature exhibition, and more than 100 special programs and events were offered throughout the year, with the celebration culminating on Founder’s Day, December 14. With leadership experience in science-focused environmental nonprofits, Jill Koski became President and CEO.


Robert J. Schillerstrom was elected Chair of the Board of Trustees. The newly constructed Firefly Pavilion opened as a facility for private rental events.


For more information about the Arboretum’s history or founder’s life, read:

A Magnificent Garden of Trees: Celebrating 100 Years of The Morton Arboretum (2022). 168-page overview of the Arboretum.

A Man of Salt and Trees: The Life of Joy Morton, by James Ballowe (2009). 287-page biography.

Both books are available for sale at The Arboretum Store.

Administration and Research Center

The Administration and Research Center has evolved to serve the changing needs of Arboretum staff and guests over several decades.

The Administration and Research Center houses research laboratories for tree science, the herbarium, the Sterling Morton Library, staff offices, and meeting rooms. The original portion of the complex was built for administration purposes in 1935, following the death of Arboretum founder Joy Morton in 1934. An auditorium for educational use was dedicated to Mr. Morton’s daughter Jean Cudahy upon her death in 1956 (the space was repurposed for contemporary meetings, programs, and events in 2016). Also in 1956, research began to take place in the building. The Sterling Morton Library, named in honor of Joy Morton’s son and Jean’s brother, opened in 1963. In 1982, an addition specifically for research was constructed. A new entrance to the Administration and Research Center opened in 2000, along with a library addition holding the Suzette Morton Davidson Special Collections (named for the granddaughter of Joy Morton and daughter of Sterling). Jean Morton Cudahy, Sterling Morton, and Suzette Morton Davidson all served in succession as Chair of the Board of The Morton Arboretum during the years 1934-1977.

Arbor Day History

Arbor Day had its beginnings in an area not always associated with trees or forests—the Great Plains.

In 1872 on April 10, Morton Arboretum founder Joy Morton’s father, living in Nebraska at the time, decided to set aside a day for planting and calling attention to trees, as the newly formed territory was a land almost entirely devoid of trees. That date became the first Arbor Day, when it is said that Nebraskans planted one million trees. The birthplace of Arbor Day was Nebraska City, where the Mortons lived in their home called Arbor Lodge. In 1885, Nebraska officially declared April 22 as Arbor Day.

Today, all 50 states, as well as many countries around the world, recognize Arbor Day in some manner. The day of its observance varies, depending on the best time of year to plant trees in each locale. In Illinois, Arbor Day is the last Friday of April.

Through the Morton family, The Morton Arboretum has a direct link to the origin of Arbor Day. Joy Morton (1855-1934) established The Morton Arboretum in Lisle, Illinois, in 1922, continuing the family legacy to plant trees.

The Morton Arboretum Logo

When Arboretum employee and artist Nancy Hart designed The Morton Arboretum logo in 1972, she was inspired by the white oak images on Morton family book plates.

The white oak (Quercus alba) is also the state tree of Illinois.

The logo is symbolic: The leaves to the left of the base of the tree represent the years that have passed. The full-grown tree signifies the present. The acorns to the right of the tree anticipate the future.