In 1948 architects Thomas Flinn, AIA, and Siberius "Si" Saito, AIA, opened their office in downtown Waterloo, Iowa. Their first project was St. Edward's Catholic Church followed by Columbus High School and Don Bosco High School. Daryl Andersen, AIA, joined the firm as a partner in 1974. Tom Flinn and Si Saito retired in 1976. Architect Robert DeVoe later merged his architectural practice with Daryl Andersen and continued the work Flinn Saito Andersen Architects had begun.
Architect Duane Svoboda joined the firm in 1979 becoming a partner in 1988. Architect Mardy Holst joined the firm in 1988 becoming a partner in 1994. Architect Steve Trost joined the firm in 1991 becoming a partner in 1996. They all have been and continue to be members of the American Institute of Architects.
In 1999 registered landscape architect Larry Kurtz, a member of the American Society of Landscape Architects, joined AHTS Architects. He became a partner in 2005 adding another dimension to the established firm.
In 2003, Jamie Castle joined the firm and became the 5th AHTS partner in 2011, enhancing the firm’s expertise in senior living.