“Penwern,” Gaelic for “great house,” was one of Wright’s first projects on Delavan Lake. As usual, he took full advantage of the natural setting. The living room opens onto a broad porch, across the full length of the house’s main block, offering a panoramic lake view. Long side-gabled roofs with wide eaves seem to make the two-story house hug the ground. The horizontal siding and the extremely broad semielliptical arches at the porch entrance and the porte-cochere underscore the low-slung effect. Uncoursed rubble in the porch piers and walls visually ties the house to the earth. The porte-cochere, with a covered walkway overhead, links the main block to an annex, in which a second-story tower thrusts through the roofline.
Fred Jones, a wealthy Chicago businessman and a bachelor, commissioned Penwern to accommodate his lavish summer parties. Besides the spacious living room, with its high, beamed ceiling and its broad-arched brick fireplace (echoing the arches outside), the first floor also featured billiards and dining rooms. Partygoers could also use the porch or head upstairs to an indoor balcony overlooking the living and dining rooms. For late-night poker games, the men retreated to the tower annex. Five upstairs bedrooms accommodated overnight guests. In 1921, when his grandmother moved in, Jones enclosed the rear porch and added a two-story wing to the house’s southwest corner. These changes did not affect the lakeside facade, though the presence of Jones’s grandmother may have affected Fred’s style of living.
The estate originally included a barn and stables; a boathouse, which fell victim to arson in 1978; and a substantial gatehouse, which housed Jones’s caretaker and more guests. Visible from the street, the gatehouse features two dormers, each embracing pairs of pointed windows. A side-gabled porte-cochere shelters the entrance to the estate and connects this gatehouse to a tower that stored water for an attached greenhouse, which no longer stands.