US Gen. George McClellan was hesitant to let his army cross a river because he was unsure how deep it was, so Captain George Custer (yes, that one) got on his horse, waded into the center of the riverbed and told him "It's this deep, sir".
Phil Sheridan saved the army from rout and they cheered his name. He told them "God damn you, don't cheer me. Fight!"
A visitor asked the Confederate Secretary of State where the State Department was. He replied, "In my hat, sir, and the archives are in my back pocket."
Gen. George McClellan, tired of Lincoln always badgering him for updates on the front, finally sent a sarcastic telegraph to the president reading "Have captured two cows. What shall I do with them?". To his surprise he got a reply back from Lincoln stating, "Milk them, George."
For that matter, Lincoln expressing his frustration with McClellan dragging his feet in attacking: "If General McClellan is not going to use the Army, I would like to borrow it for a while."
One Southern politician who objected to South Carolina's secession.
"It's too small to be a republic and too large to be an insane asylum".
Army Gen. Nathaniel Banks trying to save his routed army at Harrisburg.
Banks: Stop, men! Don't you love your country?
Private: We do, by God, and we're trying to get back to it as quick as possible!
Rebel soldiers in Col. Bradley T. Johnson's and Col. Leroy A. Stafford's brigades fired so much that they ran out of ammunition and resorted to throwing large rocks at the 24th New Yorker brigade, causing occasional damage, and prompting some of the surprised New Yorkers to throw them back. The rebel defense had barely held out against the army attack.
After Fort Sumter's surrender, a rebel soldier accidentally drank poison that he thought was medicinal whiskey. The fort's chief surgeon pumped his stomach. He then said he wasn't helping the man, just "taking back stolen federal property".
A US Army general got carried off by an observation balloon during the Peninsula campaign "quicker to the rebel capital than the entire Army of the Potomac".
Also in the Peninsula campaign, a US Army officer recalled seeing a mule sink down to its ears into a muddy Virginia road, though he later said "It was a small mule".
During the Atlanta campaign, US Army Captain Brownlow and his men crossed a river naked but saw an enemy position so near that they didn't waste time putting on their clothes before charging it. They captured four men and "they could have gotten more but the rebels had the advantage of running through the bush with their clothes on."
After the Army's defeat at First Bull Run, General-in-Chief Winfield Scott was presented by a subordinate with a (false) report that rebel troops were about to enter Washington. He scoffed, "We are now testing the fruits of war and learning what a panic is. We must be prepared for all kinds of rumors. Why, we shall soon hear that Jefferson Davis has crossed the Long Bridge at the head of a brigade of elephants."
Even funnier when you remember that President Lincoln turned down an offer of war elephants during the war.
"You men volunteered to be killed for country, and now you can be!"
When Abraham Lincoln heard complaints about General Grant's drinking, he asked what brand Grant drank. Why? “Because, if I can only find out, I will send a barrel of this wonderful whiskey to every general in the army.”