William Donovan, Joseph Kennedy, and James Forrestal were descendants of famine immigrants. By 1945, the centenary of the famine, they had not only surmounted the working-class status typical of Irish Catholics but scaled the bastions of the WASP elite.

Donovan, a prominent New York lawyer; headed the Office of Strategic Services (O.S.S.), forerunner of the Central Intelligence Agency. His grandfather had left Cork in 1847, landed at Grosse île in Canada, settled in Buffalo, New York, and been active in the Fenians, the secret Irish revolutionary organization.

Kennedy’s grandfather, Patrick, had left his small holding in Wexford in 1848 and died a poor man in Boston a decade later. Grandson Joe became a wealthy businessman and served as the first chairman of the Securities and Exchange Commission. He was the highly controversial ambassador to Britain from 1938 to 1940.

When James Forrestal’s grandfather died in Cork during the famine, his widow left her infant son with relatives and sailed to America to find work. She brought her boy over several years later. Forrestal, that boy’s son, made a fortune on Wall Street and became Undersecretary of the Navy in 1940, then Secretary in 1944.

Donovan, Kennedy, and Forrestal attended Ivy League schools. Forrestal and Donovan married wealthy Protestants. Forrestal distanced himself from his Irish Catholic relatives. (His sons didn’t meet their father’s family until his funeral.) Donovan, who as the most decorated American officer in World War I earned the nickname “Wild Bill,” was a Republican. (President Hoover passed him over for Attorney General in the belief the country wasn’t ready for a Catholic in that position.)

In 1949 Forrestal resigned as the first Secretary of Defense. Exhausted from his work, and haunted by his own personal demons, he killed himself soon afterward. Donovan left the O.S.S. in 1945 but remained an influential presence in the postwar intelligence community. Though Kennedy’s public career went into eclipse after his stint as ambassador, he hoped his son Joe would be the first Irish Catholic President. When Joe Jr. was killed in the war, the mantle passed to his brother Jack.

At war’s end Jack Kennedy returned to Boston to run for Congress. His entry into the White House in 1961 symbolized, as no other event could, the final arrival of the famine’s children in America.

—P.Q.