During the past three decades - as technological change and the relocation of production overseas and to "open shop" states increasingly reduced the relative weight and bargaining power of the organized industrial working class in the US - there have never been 100 or more major strikes in a single year.
Between 1947-1981, there had never been fewer than 100 work stoppages in any one year.
In 1949, there were 262 major strikes or lockouts involving more than 2.5 million workers and resulting in more than 43 million workdays lost. In 1959, 1.3 million workers downed tools in large workplaces. In 1969, 412 enterprises employing 1.5 million workers were shut down. There were major work stoppages in 235 workplaces employing more than a million workers in 1979. Strike activity during this period peaked in 1974, as 1.8 million workers in 435 plants and offices reacted to the oil price shock.
http://www.bls.gov/news.release/pdf/wkstp.pdf