Kempner was elected a director of the Galveston Cotton Exchange and served continuously as either director, president, or vice president of that organization for nearly fifty years. He served as Galveston finance commissioner from 1901 to 1915 and as mayor from 1917 to 1919. In 1906 he and W. T. Eldridge acquired a 12,000-acre sugar mill, plantation, and refinery in Sugar Land. They operated under various names from that time, continually expanding their control over the sugar-refining industry, until they held a virtual monopoly by the 1930s. After Eldridge's death in 1932 the Kempners consolidated this venture under family ownership and the name Imperial Sugar Company. Kempner and his youngest brother, Stanley, also took over the Texas Prudential Insurance Company. The brothers were active in banking and held a controlling interest in United States National Bank in Galveston, where Lee Kempner was CEO. In 1902 Kempner married Henrietta Blum; they had five children. Kempner died on August 1, 1967, in Galveston and was buried in the Hebrew Cemetery there.
29° 17.566, -094° 48.841
Hebrew Benevolent Society Cemetery