Robert Putnam says that there's a long "civic" generation - a generation of Americans substantially more engaged in community affairs and substantially trusting than those younger than they - which is roughly those the generation born between 1910 and 1940. The culminating point of the generation is the 1925-1930 cohort - "Since national surveying began, this cohort has been exceptionally civic: voting more, joining more, reading newspapers more, trusting more. As the distinguished sociologist Charles Tilly (born in 1928) said in commenting on an early version of this essay, 'We are the last suckers.' "
Elsewhere in the essay, Putnam examines a bunch of factors and then blames TV for the decline in civic engagement in America.