Red Annex, or "the Annex", is a part of the so-called Red House portion of Hardin House, both given their names owing to the red brick veneer added in 1955 to Red House.
Hardin House, established in 1937, underwent an expansion in the mid 1960s under Richard D. Hardin, son of founder Stella. The Apartments, an existing apartment house, was purchased in 1965, near Green House that was bought in 1963, and adjacent to where Main House was built in 1966.
Grant House is the most recently remodeled building at Hardin House. The building underwent extensive remodeling in 1998, and was then renamed Grant House in honor of Mrs. Coleen Grant Hardin who resides nearby in Austin, Texas.