Another period of expansion occurred following World War II as returning veterans used their GI Bill education benefits to attend college. The "Freshman Hill" residence complex was opened in 1953 followed by the completion of the Commons Dining Hall in 1954, two more halls in 1958, and three more in 1968. In this same time frame (1966) Herta Regina Leng was appointed as RPI's first female full professor. She is now honored there with an annual lecture series. In 1961, there was major progress in academics at the institute with the construction of the Gaerttner Linear Accelerator, then the most powerful in the world, and the Jonsson-Rowland Science Center. The current Student Union building was opened in 1967.