Officials said Platt, 91, was the wife of founding president and physics professor Joseph Beaven Platt who helped establish the college in the 1950s and decades later.
The Platts left Harvey Mudd College in 1976 and became president and first lady of Claremont Graduate University for five years, officials said.
As an officer of Campus Women, one of Foothill Philharmonic's founding members and a member of the ARCS Foundation, Jean Platt stayed active in the Claremont community, 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," said Harvey Mudd College President Maria Klawe in a statement. "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. I am so thankful to Jean for all that she has done for Harvey Mudd College and the community at large."
Her husband Joe preceded in her death on July 10, 2012 and they are survived by two daughteres, Ann Platt Walker of La Jolla and Elizabeth Platt Garrow of Willowbrook, their husbands and four grandchildren.