The Civil War defined generations of Americans and decades of politics from its end in 1865 well into the twentieth century.
In addition to catapulting the Republicans into political dominance on the national level for years after the war, it set up the issues to be debated for the next century.
There are the obvious ones that came directly after the war:
What is the status of freed slaves?
What is the Federal Government's responsibility in protecting the rights of freed slaves?
What is the status of the states that seceded from the Union? Are they states or are they a conquered territory? Do they have the right to self government anymore?
If Southern territories are made states again, can they be made to pay reparations for the war they started?
There were the ones that came later:
What is the financial obligation of the Federal Government to the Union Veterans? Should it take care of their retirement and medical care?
Can politicians and generals that served in the Civil War for the Confederacy serve again in the Congress and U.S. Army?
How long should the Democrats be kept out of power in the voting box? (Almost all Confederate Sympathizers in the South were democrats)
Should hay be made of politicians that didn't serve in the Civil War because they purchased 'substitutes' to serve in there place? (Think of Vietnam and Clinton not serving)
And the ones that would come much later:
Is the Confederate flag something that can be flown with pride or is it just a racist symbol? (South Carolina has it on its state flag to this day.)
If the Southern states will not suppress the KKK terrorizing its black and non democrat citizens, is the Federal Government obligated to send agents and troops to intervene? (again)
At what point could Southerners call themselves patriotic Americans again without being chastised by their friends? (for the generation in the South that fought the Civil War, the federal government was still viewed largely as the enemy.
Many of these questions are still being asked and Garfield fit squarely in the middle of the presidents that served in the Union military, with Johnson, Grant and Hayes before him and Arthur, Benjamin Harrison and McKinley after him.
While World War II largely defined America's place in the world, the Civil War defined domestic policy debates we have to this day.