Gamma Alpha started as a scientific fraternity in the early part of this century. At first it was just a professional organization that held meetings and invited speakers. Later Gamma Alpha bought a house over near the North Engels building. Then, rumor has it, the university wanted some land, and the people who owned that land didn’t want to leave the neighborhood, so the realtor asked Gamma Alpha if they wanted to move. And so Gamma Alpha moved to the current location. The house itself was probably built in 1920 and originally housed a single family and servants.
During those early years, Gamma Alpha housed up to 40 male Chemistry graduate students, but they didn’t eat there. Fortunately, things improved over time. In the 1970s, Gamma Alpha became a cooperative house, and now female and male students from different disciplines live here, each having their own room.
Gamma Alpha Ann Arbor is part of the “national” Gamma Alpha Graduate Scientific Society, which was founded in 1899. Once a organization with a dozen houses, it has today only three chapters: Ann Arbor, Chicago, and Ithaca. You can read more information about the society in its Wikipedia article.