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National Museum of Nuclear Science & History

Katherine “Kitty” Oppenheimer

BotanistLos Alamos, NM

ScientistSpouse to Manhattan Project WorkerWoman Scientist
Kitty Oppenheimer, Photo Courtesy of J. Robert Oppenheimer Memorial Committee

Katherine “Kitty” Oppenheimer, born Katherine Puening (1910-1972) was a German-American botanist and wife of Los Alamos Scientific Director J. Robert Oppenheimer.

Kitty was briefly a lab technician at Los Alamos under the supervision of Dr. Louis Hempelmann, but quit after a year. As a trained botanist, Kitty felt stymied professionally at Los Alamos, and instead she led an active social life. She often hosted cocktail parties for small groups of women to provide a distraction from the high-pressure environment of Los Alamos.

Kitty was also an important confidant for her husband. Robert Oppenheimer trusted his wife completely and frequently sought her advice on a host of issues facing the Manhattan Project. Kitty and her husband relied on each other for a solid foundation in the chaotic years of the Project and in their newfound celebrity in the years to come.

The Oppenheimers had two children: Peter and Toni. Toni, the younger child, was born in Los Alamos in a seven room hospital that had been dubbed “RFD,” for “rural free delivery” due to the high amount of births that occurred within the Project’s first few years. Kitty’s own fiery personality was tested by raising her two children in the unique setting of Los Alamos, before the family moved to Princeton, New Jersey following the war.


Early Life

Katherine Puening was born on August 8, 1910 in Recklinghausen, Germany and moved to America at the age of two. Her family had a noble background, and as a child, she would occasionally receive letters addressed to “Her Highness, Katherine.” Kitty entered university a few times in the early 1930s, but dropped out and married her first husband Frank Ramseyer in 1932. However, the marriage did not last, and Kitty received an annulment from the state of Wisconsin in 1933.   

Kitty was married a total of three times before she met Oppenheimer, the second marriage being to a young Communist named Joe Dallet in 1934. The couple moved to France, and Dallet joined the Communist forces fighting in the Spanish Civil War. He was killed in combat in 1937, spurring Kitty to return the United States and pursue a degree in botany at the University of Pennsylvania, which she completed with honors in 1939. She met Oppenheimer that same year while married to her third husband, a British doctor named Richard Harrison. Kitty divorced her husband and married Oppenheimer on November 1, 1940. The couple lived in Pasadena, California before moving to Los Alamos for the Manhattan Project.


Later Years

Kitty’s checkered past became an important consideration in the Oppenheimer security hearing in 1954. She had been questioned and monitored by security personnel at Los Alamos, and was the most obvious link between Robert and Communism. Both Robert and Kitty Oppenheimer affirmed their loyalty to the United States in testimony to the Atomic Energy Commission, but in the end, Oppenheimer was forced to forfeit his security clearance, effectively ending his career in government.

Robert and Kitty remained reliant on each other after the trial as Robert maintained his academic life at the Institute for Advanced Study in Princeton.  Beginning in 1954, the Oppenheimer family spent a few months every year on the island of St. John in the Virgin Islands. After a decade of relatively peaceful life, Robert developed throat cancer and passed away in early 1967. Kitty held a private ceremony for her husband, and spread his ashes in the sea outside of their home in St. John, an area known today as “Oppenheimer Beach.”

Following the death of her husband, Kitty decided to move-in with long-time family friend Robert Serber, and the two planned a round-the-world sailing trip in 1972. However, shortly after embarking in October of that year, Kitty became seriously ill and passed away in Panama City, Panama due to a pulmonary embolism.

For further reading on the lives of Kitty Oppenheimer and her husband, check out American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer written by Kai Bird and Martin Sherwin. 

Katherine “Kitty” Oppenheimer's Timeline
1910 Aug 8th Born in Recklinghausen, Germany.
1932 Married her first husband, Frank Ramseyer. The couple divorces one year later.
1934 Married Joe Dallet and moved to France.
1937 Returned to the United States after Dallet is killed in the Spanish Civil War.
1939 May Received B.A. with honors in botany from the University of Pennsylvania.
1939 Aug Met J. Robert Oppenheimer at a garden party. The two begin to date despite Kitty being married to Richard Harrison.
1940 Nov 1st Married Oppenheimer the day after officially divorcing Harrison.
1954 Apr Testified in the Oppenheimer security hearing to defend her husband.
1972 Oct 27th Died in Panama City,Panama due to a pulmonary embolism.

Badge photo from Los Alamos

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