One of upper Napa Valley's longest running spas is passing to new ownership after nearly seven decades.

The 42-room Dr. Wilkinson's Hot Springs Resort at 1507 Lincoln Ave. in Calistoga has been sold to San Francisco-based Chartres Lodging Group for an undisclosed amount, according to an April 8 announcement. Included is the bath house with mud baths and and pools fed by natural hot mineral springs.

"After 66 years of service to our guests, employees, and community through our parents’ vision, we are excited to pass the resort to a uniquely qualified owner and operator that appreciates and will build upon the foundation that our family has laid in the world of health and wellness,” said Carolynne Wilkinson Clair of seller Wilkinson Family LLC in the news release.

Another descendant, Mark Wilkinson, noted how late Dr. and Edy Wilkinson helped Calistoga become a globally recognized resort area.

The Wappo tribe first discovered the volcanic hot springs near Mount St. Helena over 500 years ago, but it wasn't until Samuel Brannan's efforts in the 1860s to make Calistoga the hot springs of the West that resorts started springing up to serve visitors, according to the city website. Then came Giuseppe Musante in the 1920s, bottling mineral water as Calistoga Beverage Company.

Robert Kline, Chartres CEO and co-founder, called it an "iconic property" and said new hospitality projects in the Calistoga area have made the site attractive. Chartres plans to upgrades the guest rooms, resort grounds and the pools. It will be managed by affiliated company Kokua Hospitality, which also runs hotels in South Lake Tahoe, Carmel, San Francisco, New York City, Honolulu and Houston.

“Our focus will be to provide a targeted level of customer experience that reflects Calistoga’s special place in Napa Valley and the growing wellness space,” said Kirk Pederson, Kokua Hospitality president, in a statement.

Chartres started in 2002 and said it has a $3.6 billion portfolio of resorts and hotels across the United States.

CBRE hotel property specialists Henry Bose Jr. and Mark McDermott represented Wilkinson Family LLC in the transaction.