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. This one-acre family burial plot was set aside by Arboretum founder Joy Morton in 1925.
The original design was formal at the center and encircled by a trail through a naturalistic arrangement of oaks, yews, and hawthorns. 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, a fountain was installed, and new plantings were added. Many of the original yews, and the three white oaks that framed the space in 1925, still remain.
Joy Morton was the first to be interred in the family plot at the base of a white oak upon his death in 1934. Others memorialized here are 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).