Final answer:
The term 'twin nightmares of the previous decades were laid to rest' likely refers to historical events that brought an end to periods of significant concern, such as the eradication of smallpox and the conclusion of Prohibition in the United States.
Step-by-step explanation:
The phrase 'twin nightmares of the previous decades were laid to rest' can be interpreted in a historical context, referring to significant concerns that were eventually overcome or resolved. In a United States historical context, it likely refers to the end of particular periods of fear or conflict that were significant in the nation's past. A notable example is the end of smallpox, a devastating disease which was eradicated in the 20th century through extensive vaccination campaigns, thus putting to rest a major public health nightmare.
Another possible interpretation involves the end of Prohibition, a period in the United States (1920 to 1933) marked by a nationwide constitutional ban on the production, importation, transportation, and sale of alcoholic beverages. This period also saw a rise in the illegal liquor trade, enforcement difficulties, and a spike in organized crime, but it concluded when the 21st Amendment repealed the 18th Amendment, ending the Prohibition era. Such resolutions of national fears can be perceived as historical milestones where the society managed to put major apprehensions and conflicts behind.