What events took place during the civil war?

In the West, the capture of Vicksburg, the last Confederate stronghold on the Mississippi.

In the East (on the same day, by chance), the devastating Confederate defeat at Gettysburg, ending Lee's hopes of invading the North, and putting him out of action till the following spring.

In Tennessee, the Army of the Cumberland came close to destruction at Chiockamauga, and was besieged in Chattanooga - saved from starvation by Grant, who was rapidly gaining enough credibility for the job of General-in-Chief, to which he would soon be appointed.