Question

During which decade did the U.S. pursue a policy of isolationism

Answer 1

1930's is the decade which the U.S pursed a policy of isolationism.

Answer 2

The United States adopted a policy of isolationism after the First World War.  They had lost many men during the conflict and did not want to get involve in another war.  They also had to deal with the Depression.  They continued this policy until the outbreak of the Second World War.