As Margaret Lyons of Vulture (and various Imgur users) noted, "Mad Men" reused a set location on "The Monolith" last night. Maraget's hippie commune appears to be identical to the place where Don lives in the "The Hobo Code" (Season 1, Episode 8). So, clearly, Don's childhood home has been bought by a bunch of hippies as part of an intricate coincidence in the "Mad Men" universe (or the producers just couldn't find another good dilapidated farmhouse).
"Mad Men" recycled a location: Margaret's hippie commune is where Don lived in "The Hobo Code": http://t.co/b5cyKiJuAo
— Margaret Lyons (@margeincharge) May 5, 2014