One good way of understanding U.S. Constitutional Law is to note the big changes in the bedrock of the terrrain, where the earthquakes shattered the land.
First came the Revolution and then the Civil War, which produced the 14th Amendment. Suddenly the promise articulated by Thomas Jefferson in the Declaration of Independence (which was poetry, not law) was redeemed, almost. It took over a hundred years and we still work at it, over opposition, daily, to overcome the effects of slavery on housing patterns, jobs, schooling, social acceptance, etc.
Abraham Lincoln, dedicating the Gettysburg Battlefield as a memorial, articulated the significance of the sacrifice in a brief address, tying it to the promise of the Revolution.
Following the Civil War and its freeing of the slaves and the promise of equality made into law for the first time, we can be said to have a new Constitution, Ver. 2.0, if you will.
Below is a broader take on the significance of Lincoln's Gettysburg Address.