At least one Boston team has won championships, in the four major sports, every decade since the 1900s, except the 1990s. And in onnly the 1970s did more than one team win a championship, when both the Celtics and Bruins won, two apiece.
(Note: I am using the common definition of "decade", which means the very first decade was from years 1 to 9, the second from years 10 to 19, and so on :-).
1903: Red Sox
1912: Red Sox 1915: Red Sox 1916: Red Sox 1918: Red Sox
1929: Bruins
1939: Bruins
1941: Bruins
1957: Celtics 1959: Celtics
1960: Celtics 1961: Celtics 1962: Celtics 1963: Celtics 1964: Celtics 1965: Celtics 1966: Celtics 1968: Celtics 1969: Celtics
1970: Bruins 1972: Bruins 1974: Celtics 1976: Celtics
1981: Celtics 1984: Celtics 1986: Celtics
2002: Patriots 2004: Patriots