It was 76 years from Washington's First Inaugural in 1789 to Lincoln's Second Inaugural in 1865. It was 76 years from the surrender at Appomattox Courthouse in 1865 to the attack at Pearl Harbor in 1941.
Going backward, it was 76 years from the First Inaugural in 1789 to the Treaty of Utrecht in 1713, which settled one of the British-French colonial wars. And going 76 years back from Utrecht takes you to 1637, when the Virginia and Massachusetts Bay colonies were just getting organized.
As for our times, we are now 71 years away from Pearl Harbor. The current 76-year interval ends in December 2017.
Each of these 76-year periods can be depicted as a distinct unit. In the colonial years up to 1713, very small numbers of colonists established separate cultures that have persisted to our times.
The story is brilliantly told in David Hackett Fischer's "Albion's Seed." For a more downbeat version, read the recent "The Barbarous Years" by the nonagenarian Bernard Bailyn.
From 1713 to 1789, the colonies were peopled by much larger numbers of motley and often involuntary settlers -- slaves, indentured servants, the unruly Scots-Irish on the Appalachian frontier.
For how this society became dissatisfied with the colonial status quo, read Bailyn's "Ideological Origins of the American Revolution."
From 1789 to 1865, Americans sought their manifest destiny by expanding across the continent. They made great technological advances but were faced with the irreconcilable issue of slavery in the territories.
For dueling accounts of the period, read the pro-Andrew Jackson Democrat Sean Wilentz's "The Rise of American Democracy" and the pro-Henry Clay Whig Daniel Walker Howe's "What Hath God Wrought." Both are sparklingly written and full of offbeat insights and brilliant apercus.
The 1865-1941 period saw a vast efflorescence of market capitalism, European immigration and rising standards of living. For descriptions of how economic change reshaped the nation and its government, read Morton Keller's "Affairs of State and Regulating a New Society."