The home of author Edith Wharton has received an anonymous $300,000 gift that will be used for operating expenses and to pay down debt. The organization that runs the 1902 Lenox mansion, known as The Mount, received the gift after the donor read about concerns over the ability to repay $1 million in principal on a loan in May. The donor was described only as a local woman. The mansion faced foreclosure in 2008. Wharton designed and built the house, where she finished her breakthrough novel, “The House of Mirth.’’ She left the estate in 1911.