1998: U.S. cryptologic pioneer Abraham Sinkov died.
Dr. Sinkov was inducted into the NSA Cryptologic Hall of Honor in 1999. Read an excerpt from his Hall of Honor entry below and click on the link at the bottom of the page to see the full entry on the NSA site.
From the Hall of Honor:
In 1930, William Friedman, a senior civilian in the Army's Signal Intelligence Service (SIS) was authorized to hire three civilians, at $2,000 per year -- a fairly good salary in the early period of the Great Depression. On April 1, Frank Rowlett, a mathematics teacher from Virginia, reported for duty. Later that month, two mathematics teachers from Brooklyn came to Washington to work as cryptanalysts, Abraham Sinkov and Solomon Kullback. In addition to his successes with SIS and also with the Central Bureau, in 1954, Dr. Sinkov became the second NSA official to attend the National War College (the first was Dr. Louis Tordella). Upon his return, he became Deputy Director for Production, effectively swapping jobs with his old colleague Frank Rowlett. Dr. Sinkov retired from NSA in 1962.