Which effect of the Civil War had the biggest impact on America after the war?
RACE.

The biggest impact of the civil war was the end of slavery.

Explanation:

The southern states had been a little aloof from the US for a long time.

This was partially because f the 'peculiar practice' and many other such things.

These were solved by might and the southern states, albeit with some resentment were brought back into the fold of the union.

At the same time, the south had to give away slavery and then the freed men also became citizens and started having an influence on the policies, albeit a minuscule one.

i receive this honor with deep gratitude and great humility. it is an award that speaks to our highest aspirations — that for all the cruelty and hardship of our world, we are not mere prisoners of fate. our actions matter, and can bend history in the direction of justice.

this is a way. : )

the answer is a) the proclamation of 1763.