Early Warning by Jane Smiley
"Early Warning opens in 1953 with the Langdon family at a crossroads. Their stalwart patriarch, Walter, who with his wife, Rosanna, sustained their farm for three decades, has suddenly died, leaving their five children, now adults, looking to the future. Only one will remain in Iowa to work the land, while the others scatter to Washington, D.C., California, and everywhere in between. As the country moves out of post-World War II optimism through the darker landscape of the Cold War and the social and sexual revolutions of the 1960s and '70s, and then into the unprecedented wealth--for some--of the early 1980s, the Langdon children each follow a different path in a rapidly changing world. And they now have children of their own: twin boys who are best friends and vicious rivals; a girl whose rebellious spirit takes her to the notorious Peoples Temple in San Francisco; and a golden boy who drops out of college to fight in Vietnam--leaving behind a secret legacy that will send shock waves through the Langdon family into the next generation."
The second of Smiley's trilogy is not quite as strong as the first part mainly due to the sheer number of characters. I had some difficulty keeping track of who was who as the book went from 1953 to the early 80's.