This two-story, clapboard structure, known as the Burdell Frame House, was built in 1874 for Mary Burdell's cousin, Mary Joynsen.
Originally a rectangle building, it has been modified with a projecting, two story addition on the end facing the parking lot, a two-story shed on the opposite end, and a single story garage at the rear. Along with the mansion this building's interior was modified into a dormitory facility when Rancho Olompali was acquired by the University of San Francisco for use as a retreat.
A large glass conservatory (green house) was once located downslope from the frame house. A swimming pool and bath house also occupied the site in the 1950's.
A portion of the building now houses the park Visitor Center and Administration Office.