The Athenaeum is a private club that opened its doors in 1930 with the intention of promoting social, cultural, and intellectual exchange. Today its members include Caltech faculty, trustees, alumni, staff, grad students, and Associates, as well as community members from the Jet Propulsion Laboratory and the Huntington. 

The upper floor includes 24 guest rooms and four suites. Guests have included luminaries such as Albert Einstein, Robert Millikan, and others.

The Athenaeum was built from proceeds of a gift in stocks and bonds from Mr. and Mrs. Allen C. Balch. The securities were transferred to Caltech in 1929, and the Institute astutely sold them before the stock-market crash. Balch was president of the Caltech Board of Trustees from 1933 to 1943.

Architect: Gordon B. Kaufman
Year occupied: 1930
Building number: 61
Building size: 57,757 gross square feet