Though Kennedy spent a great deal of time on the West Coast due to his involvement in the film industry, back east, his family continued to expand. His third daughter, Eunice was born on June 10, 1921, with Patricia following on May 5, 1924, Robert (Bobby) on November 20, 1925 and Jean on February 20, 1928. In 1926, he moved the family from Boston to Riverdale, New York. Kennedy also continued his interest in real estate by purchasing property in Palm Beach, Florida, and Hyannisport, Massachusetts. Kennedy avoided the stock market pitfalls of 1929. He had largely pulled out of the market before the infamous October crash and the family's finances remained largely unaffected throughout the 1930s. The Kennedy family was completed with the birth of their ninth child, Edward (Teddy) Moore on February 22, 1932.
It was in the 1930s that Kennedy began to devote his time to politics, lending both financial and personal support to Franklin Roosevelt's 1932 presidential campaign. In September 1932, Kennedy spent several months with Roosevelt on his campaign train. During a 1933 trip to Europe with Jimmy Roosevelt (FDR's son), Kennedy became involved in the import business and became the U.S. agent for Haig & Haig Ltd., John Dewar and Sons, Ltd. and Gordon's Dry Gin Company Ltd.. With these new contacts, Kennedy arranged for his company, Somerset Importers, to stockpile liquor imports for the end of Prohibition. In July 1934, Kennedy returned to politics after Roosevelt appointed him chairmen of the newly created Securities and Exchange Commission (SEC). Despite widespread qualms about the appointment of an ex-speculator to an influential regulatory position, Kennedy got the SEC off to a firm start. His knowledge of and ties with the business community were an asset in an agency charged with policing investment practices. Though Kennedy had been appointed for a five-year term, he resigned from the SEC in September 1935. After taking a six-week tour of Europe and reporting to Roosevelt on the European economic situation, he began work as a corporate consultant with David Sarnoff at R.C.A. Kennedy also returned briefly to the movie industry as an advisor to Paramount Pictures. He prepared an influential report that led to changes throughout the company's operational structure. During the 1936 presidential campaign, Kennedy published and widely distributed I'm for Roosevelt. Written with the aid of New York Times columnist Arthur Krock, the book detailed Kennedy's strong support for Roosevelt and the New Deal from the prospective of the business community. After his successful re-election, Roosevelt appointed Kennedy chairman of the Maritime Commission. Created by the Merchant Marine Act of 1938, the commission was expected to rejuvenate America's merchant shipping industry, which had been crippled by an outdated fleet and a difficult labor situation. Kennedy spent only ten months at the commission. In early December 1937, the news broke that Roosevelt had selected Kennedy as the new ambassador to the Court of St. James’s, a position Kennedy had had his eye on for several months. Kennedy officially resigned from the Maritime Commission in February 1938.
Kennedy served as ambassador to Great Britain from 1938 until 1940. During this time, Kennedy argued for appeasement and for American neutrality, wanting the United States to stay out of any conflict that might occur between Britain and Germany. Kennedy resigned in November 1940. The 1940s were a hard time for the Kennedy family. During the war, Kennedy’s two eldest sons served in the Navy, Joe, Jr. as a pilot and John as the commander of PT-109. In 1944, Joe, Jr. was killed in a bombing raid over Germany. John was seriously wounded when his boat was attacked by the Japanese. On May 14, 1948, Kennedy’s daughter Kathleen died in a plane crash over Sainte-Bauzille, Ardeche, France. When her father had served as ambassador, Kathleen had met and married William John Cavendish, Marquess of Hartington, who was also killed in action in World War II in 1944.
In his later years Kennedy continued to be successful in business (notably real estate) and devoted considerable time to philanthropic activities, especially the Joseph P. Kennedy, Jr., Foundation. After his eldest son’s death, Kennedy focused on the career of his second son, John F. Kennedy, convincing him to run for a seat in Massachusetts’ eleventh congressional district, which he won in 1946. John F. Kennedy served three terms (1947-1952) in the House of Representatives, two terms (1952-1960) in the U.S. Senate, and was elected President of the United States in 1960. Kennedy also supported the political aspirations of his son Robert, who served one term (1965-1968) in the U.S. Senate.
On Dec. 19, 1961, Joseph Kennedy suffered a series of strokes (coronary thrombosis) that left him an invalid. Weathering the tragedies of the assassinations of his sons John and Robert, Kennedy bore his burden quietly. On November 18, 1969, Joseph P. Kennedy died in Hyannis, Massachusetts, at the age of 81.