One of the region's largest undeveloped jewels - a 1,500-acre property in rapidly growing northern Chester County - is on track largely for preservation, with minimal home building.

The Natural Lands Trust reached an agreement of sale on Bryn Coed Farms after negotiating with the family that owns it - heirs to the Luden's cough drop fortune - for more than five years, the regional land conservation group announced.

The purchase has yet to be finalized, but the agreement clears the way for the trust to continue meeting with private and public funders and municipal officials, and to conduct environmental testing on the tract, which trust president Molly Morrison called "a community and ecological treasure."

About 900 acres is active farm or meadowland in a county among the fastest growing in Pennsylvania. The property also includes rolling hills, wetlands, and forests. It "embodies all of the elements of the traditional landscape" of Chester County, Morrison said.

She declined to say how much money the group agreed to pay, citing a confidentiality agreement with the owners, but she said the amount may be released at a later date.

Bryn Coed Farms grew from acquisitions in the 1960s by philanthropist brothers and Luden's heirs William, Daniel, and H. Richard Dietrich Jr. The property includes the former homestead of Owen J. Roberts, associate justice of the U.S. Supreme Court from 1930 to 1945.

If the sale goes through as planned, the conservation group wants to form a nature preserve spanning more than 400 acres, with eight miles of hiking trails. The tract sits in East and West Pikeland and West Vincent Townships. The largest portion is in West Vincent, which is considering establishing a 72-acre municipal park.

The rest of the property would be divided and sold to private individuals, with conservation easements restricting future development to one home per 50 acres, according to Natural Lands Trust. Current zoning allows for nearly 700 homes on the land.

Toll Bros. was among several developers interested in the property.

"The idea is to protect as much of the land as possible from development, and if development has to occur, it will be in a very limited manner," Morrison said.

The amount of land the trust can preserve as open space depends on how much money it can raise, she said.

H. Richard Dietrich III said his family was proud to see the land preserved and "thrilled" to partner with Natural Lands Trust.

"The long-term vision in all of this is that it would remain open space," Dietrich said. "Everybody recognized just how special a place it was."