High up in the Santa Monica Mountains of Brentwood, with sweeping city and ocean views, this historic home is one of the most important of the small number remaining from this forward-looking postwar housing experiment. Still owned by the original family, one of four founders of the Mutual Housing Association, this home was literally the first built among 500 planned for this award-winning neighborhood. The architecture is elegantly simple, with form following function: a low-slung roof with tongue-and-groove ceilings held aloft by exposed beams and slender posts, creating clerestory windows on two sides. Eight-foot sliding glass doors allow the open plan to flow freely outdoors to patios and private gardens, creating the illusion of a home twice its actual size. Eligible for Mills Act status, which would save thousands of dollars annually in property taxes.