The Trowbridge House, at 708 Jackson Place, is one of the rowhouses facing Lafayette Square on the west side. It was built in 1859 for mathematician William Trowbridge, in the Italianate style.
The government leased it starting around 1900, and purchased it in 1950. It has been used for a variety of Federal offices. The current plan is to use it as a guest house for visiting former Presidents, and to connect it to Blair House through the garden and the basement.