For thousands of years, the native Lenni Lenape tribe fished its streams, hunted its forests, and planted its fields.

[4] In 1700, a Quaker farmer named George Peirce purchased 402 acres (163 ha) of this English-claimed land from William Penn's commissioners.

[6] By 1850, the arboretum boasted one of the finest collections of trees in the nation and had become a place for the locals to gather outdoors—a new concept that was sweeping America at the time.

[6] The Pennsylvania guide noted in 1940 that "Longwood received its present name from 'Long Woods,' as the section was known before the Civil War, when black slaves fleeing from the South found shelter in this station on the Underground Railroad, which was supported by Quakers of Kennett Square, Hamorton, and Wilmington, Delaware.

The farm passed out of the family through several hands in quick succession, and a lumber mill operator was about to cut down the trees for timber in early 1906.

On July 20, 1906, 36-year-old du Pont purchased the farm primarily to preserve the trees, in a transaction managed by Isabel Darlington, Chester County's first female lawyer.

It lies in front of the historic Longwood Progressive Friends Meeting House, founded by Quaker dissidents in 1854 and acquired by Pierre S. du Pont after it closed in 1940.

[12] In 2024 Longwood Gardens acquired Granogue, a 505-acre (204 ha) cultural landscape in Wilmington, Delaware and one of the last remaining unprotected pieces of open space in the Brandywine River corridor.

The founder of West 8, Adriaan Geuze, stated their mission is: "to celebrate Longwood, enjoy it, keep it, preserve it, while asking how it could function as a spectacular place for larger groups of people in the 21st century."

Joshua and Samuel Peirce collected many native and exotic trees, which they planted in straight rows on land east of their farmhouse.

Peirce also added a historical marker for Hannah Freeman, purportedly the last surviving member of the Lenape people, who had been born in the area in 1731.

[6] Visitors to Longwood Gardens today still enjoy Peirce's Park, which is now punctuated by the Sylvan Fountain, added by Pierre S. du Pont in 1925–27.

[20] In 1914, Pierre S. du Pont added the Open Air Theatre after visits to the Villa Gori in Siena, Italy, provided inspiration.

[21] From 1925 to 1927, du Pont designed and constructed the Italian Water Garden on a site northeast of Longwood's Large Lake, after gaining inspiration from a visit to the Villa Gamberaia, near Florence, Italy.

[24] In the 1970s, landscape architect Thomas Church was engaged to advise Longwood on long-range planning, garden improvement, and visitor circulation.

[25] By 1977, Thomas Church could no longer visit because of his declining health, and the English designer Sir Peter Shepheard became Longwood's consulting architect.

[26] In 1995, landscape architect W. Gary Smith designed Peirce's Woods as an "art form" garden that brings together the most ornamental characteristics of the eastern deciduous forest.

Thousands of native plants were added, including 10,000 rescued from the North Carolina mountains prior to impending highway construction.

The Meadow Garden is actively propagated with herbaceous perennials and includes other interventions to manage invasive plants, control trees and shrubs, and promote wildlife.

With the November 2024 opening of Longwood Reimagined, new features include the 32,000-square-foot West Conservatory, featuring interior Mediterranean-inspired gardens set amid pools, canals, and fountains; the preservation and relocation of the Cascade Garden—the only design in North America by Roberto Burle Marx—in its own 3,800-square-foot custom glasshouse; a new outdoor Bonsai Courtyard; refreshed Waterlily Court; new 1906 restaurant and The Fountain Room event space overlooking the Main Fountain Garden; new central hub with studios, a library, and staff offices called The Grove; and a preserved and expanded Orchid House.

Longwood's first conservatory was built in 1914 when Pierre S. du Pont added an L-shaped extension to the original Peirce farmhouse, doubling its size.

It draws upon the extensive photographic and manuscript resources now stored at the Hagley Museum and Library to show the entire 300-year history of the property.

It provides free K-12 programs for students and educators that are tied to Next Generation Science Standards, and its high school offerings focus on such topics as environmental stewardship, biodiversity, and plant propagation.

Internships for international students are offered in the areas of education, library science, marketing and public relations, and ornamental horticulture.

[77] The Longwood Fellows Program is a 13-month residential and working experience that helps refine the skill level and heighten the self-awareness of leaders within public horticulture.

The 1,500-seat Open Air Theatre marked its 100th anniversary in 2014, having hosted more than 1,500 performances over the years, including theater troupes, Broadway-style musicals pageants, choruses, and the United States Marine Band.

It was originally constructed in 1929 to house Longwood's pipe organ and to serve as a venue for concerts, lectures, and dinners, a tradition that continues today.

The Ballroom is architecturally unique for its parquet floor, fabric-paneled walls, and ceiling made of 1,104 panes of rose-colored etched glass.

[83] The Exhibition Hall has hosted hundreds of performing artists, including the Meyer Davis[84] dance band, Metropolitan Opera sopranos, John Philip Sousa, and South African vocal groups.

Once used by the du Ponts for dances and dinner parties, the sunken marble floor is typically flooded with a few inches of water to reflect seasonal displays.