Gamma Alpha started as a graduate scientific fraternity in the early part of the last century. In its beginnings, the group was a professional organization that held meetings and invited speakers. Gamma Alpha later bought a house over near the North Engels building. Rumor has it that the the university wanted to buy land, and the people who owned that land did not want to leave the neighborhood. The realtor asked Gamma Alpha if they wanted to move, and thus, Gamma Alpha moved to its current location. The house itself was built in circa 1919 and originally housed a single family and servants.
During the early years, Gamma Alpha housed up to 40 male Chemistry graduate students, who did not eat in the house. In the 1970s, Gamma Alpha became a fully-livable 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. The Ann Arbor chapter was chartered on April 18, 1913. Notable alumni include George M. Curtis, the president of the University of Michigan from 1929-1951. 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.