HISTORICAL VALUE

Rock Hill Farm
 

18th century: Benjamin Cox and the Quaker origins

Rock Hill’s documented history reaches back to Benjamin Cox, described as one of Willistown’s founding Quakers. The property developed over generations from an agricultural holding into a substantial country estate. Contemporary accounts identify Cox as one of the property’s original owners. 
 

Late 19th / early 20th century: the estate takes shape

By the late 1800s and early 1900s, Rock Hill had become a significant country estate. The present principal residence dates to approximately 1900, and the property accumulated additional houses, barns, stables, greenhouses, a springhouse, tea house and other agricultural and estate structures. The Chester County 1883 Historical Atlas identifies Rock Hill as a contributing historic resource, and Willistown’s Historical Commission has identified at least four principal historic resources on the property. 
 

Robinson family / Acme Markets connection

Rock Hill was subsequently part of the extensive Robinson family estate holdings. The Robinson brothers—immigrants from Ulster, Ireland—founded Acme Markets in 1917. Their family accumulated substantial landholdings on the Main Line, including Nawbeek, which incorporated Rock Hill Farm, as well as other major estates in the area. 
 

Colket family: approximately 1985–2021

The property ultimately came into the hands of the Colket family. According to reporting about the property, the Colkets acquired Rock Hill in 1985. Tristram C. Colket Jr. and his wife, Ruth M. Colket, were the owners for nearly three decades. 

Tristram Colket was the grandson of John T. Dorrance Sr., founder of Campbell Soup Company. During the Colkets’ ownership, Rock Hill remained a large, largely intact estate, with its historic buildings, farmland, woods, streams and wetlands preserved together. 

Importantly, Willistown Conservation Trust had discussions with both the former and current owners about protecting Rock Hill’s conservation values. WCT reported in 2022 that it had been interested in protecting the property for years and had explored conservation options with the former owners before the sale. 
 

2020–2021: offered for sale

After Tristram Colket’s death, the property was placed on the market in 2020. It was initially listed for approximately $38 million. The estate comprised roughly 246 acres in the broader property description, including the historic core around South Valley Road and Grubb Road. 

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December 2021: purchased by Rockhill Farm Acquisitions LLC

The pivotal ownership change occurred in December 2021, when Rockhill Farm Acquisitions LLC, an entity affiliated with Philadelphia-area developer J. Brian O’Neill, acquired the property from Ruth M. Colket.

The recorded transaction price was approximately $25.48 million. Contemporary reporting identifies the property as approximately 246 acres, although subsequent planning documents and litigation sometimes refer to the principal tract as 222 acres plus an adjacent 24-acre parcel. 

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2022–present: development and preservation conflict

Following the purchase, Rockhill Farm Acquisitions proposed subdivision and residential development. Earlier proposals contemplated more than 20 luxury homes, prompting the formation of the Save Rock Hill Farm campaign and substantial community opposition. 

The property subsequently became the subject of years of township review and litigation. In July 2026, a Chester County judge reversed Willistown Township’s 2024 denial of the developer’s preliminary plan. 

As of August 2026, the township and developer were discussing a potential settlement that could preserve a substantial majority of the land while allowing residential development on part of the property. The Township held a special public meeting on August 20, 2026, but took no action at that meeting. 

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The larger historical story

What makes Rock Hill particularly compelling is that this isn’t simply a story about a property changing hands. It is a transition from an agricultural and historic landscape that remained substantially intact for generations to a development proposal involving the same land.

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Here's the ownership timeline:

Benjamin Cox / early Quaker ownership
↓
Historic estate development — 18th/19th centuries
↓
Robinson family / Acme Markets fortune
↓
Colket family — acquired 1985
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Ruth & Tristram Colket — approximately 1985–2021
↓
Rockhill Farm Acquisitions LLC / J. Brian O’Neill — December 2021–present