[1] Erickson was born in Oak Park, Illinois a suburb of Chicago, where her father was a Swedish Lutheran minister.

She graduated from Augustana College at Rock Island, Illinois in 1945, and from Cornell University with a MA and a PhD.

From 1976 to 1978, she was the Sherman Fairchild Distinguished Scholar at the California Institute of Technology.

In 1982, she was the Paul Mellon chair of American History at Cambridge University.

In 1952, Erickson returned to England to marry Louis Watt; they had two sons, Tom and David; their marriage was dissolved in 1992.