Delchester Farm is located in the center of The Okehocking Land Preserve. The Okehocking Indian Land Grant Historic District presents a collection of 18th and early 19th century farmhouses and their farm outbuildings in a rural setting and was listed on the National Register of Historic Places in 1993. The Okehockings, a band of Lenape Indians, petitioned William Penn and in 1703 were granted a 500-acre tract at the center of the District. The original Indian Land Grant lies on a diagonal between West Chester Pike and Goshen Road with elevations from 250 to 400 feet, and the most level area is a plateau in the center of the District on either side of Delchester Road.
By the mid-1720s, the Indians had drifted away from their Grant and then in 1737, the land was reallocated to Amos and Mordecai Yarnall. In 1749, Amos Yarnall's son, Daniel, inherited his uncle Mordecai's property and then in 1786, Daniel bequeathed it to his grandson, Thomas Willing.
Delchester Road was run through the center of the Indian land over a well-worn Indian trial and was the first recorded road in Willistown Township.
After the mid-1800s, with a contraction of agricultural profitability, the farms were either sold by widows or at Sheriff's sales. The growth of industrial fortunes paralleled this decline until early 20th century "gentlemen farmers" were drawn to the area. These wealthy Philadelphia businessmen desired country estates reflecting their place in society and began to assemble the fragmented farms into large country estates in the manner of English nobility.
In 1913, Dr. Thomas Ashton, a psychiatrist who had married the heiress to the Baldwin Locomotive fortune, assembled most of his 1400-acre Delchester Farm. This estate included the 350-acre Mordecai Yarnall 1737 Farm, which became the nucleus of the complex.
Ashton called the aggregate estate "Delchester Farms." Ashton chose as his home the Mordecai Yarnall 1737 Farm, expanded its already large array of farm buildings and improved and enlarged the main house. This property became the centerpiece of his estate. Ashton also stabilized and improved the buildings on all his other properties.