Characteristic elements of Twin Oaks' Georgian-style architecture include a portico-inspired carriageway, central Palladian window, and twin chimneys flanking the main roof

After construction, Mrs. Hubbard described the house to a friend, “We bought a place several miles from Washington which we call ‘Twin Oaks’ from two beautiful oaks in front of the house, and the last year and a half we have been building a summer house into which we just moved. It is a large, pleasant, open house with a beautiful view of the trees and woods and country on all sides. On the North are woods, on the South, the Potomac, the [Washington] Monument, and the Capitol.”

For many years, the estate was a gathering spot for the Hubbard family and their guests, including suitors for their two daughters, Mabel and Grace. Mabel, who had lost her hearing as a young child due to scarlet fever, married Alexander Graham Bell, whose method for educating the hearing impaired had caught the attention of Gardiner Green Hubbard. Bell’s later development of the telephone was enabled in part through financial support from Hubbard, and an early prototype of Bell’s phone can still be seen at Twin Oaks today in the upstairs study. After their parents passed away, Mabel and Grace inherited the estate. Mabel and Alexander soon sold their half of the estate to Grace and her husband Charles Bell, Alexander’s cousin and founder of the Bell and Company Bank, who continued to reside there until Grace began renting the estate to prominent individuals in the 1930’s.