I never learned my Civil War history very well, but I did notice that this week was the 150th anniversary of the Battle of Pittsburg Landing.
The Wikipedia article sums the 3-day event up as follows:
The two-day battle of Shiloh, the costliest in American history up to that time, resulted in the defeat of the Confederate army and frustration of Johnston's plans to prevent the joining of the two Union armies in Tennessee. Union casualties were 13,047 (1,754 killed, 8,408 wounded, and 2,885 missing); Grant's army bore the brunt of the fighting over the two days, with casualties of 1,513 killed, 6,601 wounded, and 2,830 missing or captured. Confederate casualties were 10,699 (1,728 killed, 8,012 wounded, and 959 missing or captured). The dead included the Confederate army's commander, Albert Sidney Johnston; the highest ranking Union general killed was W. H. L. Wallace. Both sides were shocked at the carnage. None suspected that three more years of such bloodshed remained in the war and that eight larger and bloodier battles were yet to come.
On his wonderful Up and Down California blog, Tom Hilton relates how the event reached California.
It's hard to comprehend nearly 25,000 casualties in a 3 day pitched battle on the shore of the Tennessee river.