Chronological History of the 20th SOS 1950s 1956 1957 1958 1959 1960s 1966 1967 1968 1969 1970s 1970 1971 1976 1977 1978 1979 1980s 1980 1981 1982 1984 1985 1986 1987 1988 1989 1990s 1990 1991 1992 1993 1994
