Platt, 91, was the wife of founding president and physics professor Joseph Beaven Platt, who helped establish the college in the 1950s, officials said.
The Platts left Harvey Mudd College in 1976 and became president and first lady of Claremont Graduate University for five years, officials said.
Jean Platt stayed active in the Claremont community, including serving as one of Foothill Philharmonic's founding members, officials said.
Additionally, she was on the board of the Rancho Santa Ana Botanic Garden and involved in retirement communities Pilgrim Place and Mt. San Antonio Gardens.
"Jean's love of HMC was an integral part of the college's early years, especially in the development of our students and alumni," Harvey Mudd College President Maria Klawe said.
"During her 20 years as HMC's first lady, she opened her home to host first-year dinners, arranged faculty teas and stood by Joe's side through the building of the college. In addition to her contributions to HMC, Jean was an energetic and faithful community volunteer."
Joe Platt preceded his wife in death on July 10, 2012.
They are survived by daughters Ann Platt Walker of La Jolla and Elizabeth Platt Garrow of Willowbrook as well as their husbands and four grandchildren.
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