Retreating from Sherman's advancing armies, Gen Joseph E. Johnston had withdrawn across the Peachtree Creek, just north of Atlanta. Johnston had drawn up plans for an attack on part of Thomas's army as it crossed the creek. On July 17, he received a letter from Confederate President Jefferson Davis informing Johnston that he was relieved from command. The political leadership of the Confederacy was unhappy with Johnston's lack of aggressiveness against the larger Union army and so they replaced him with Hood, who had a reputation for bravery. Hood took command and carried out the battle. The Union troops, after crossing the creek, were assaulted by the Confederate army. The Union center was driven back, but ultimately held and the Confederate troops were forced to call off the attack at sunset. Estimated casualties were 6,506 in total: 1,710 on the Union side and 4,796 on the Confederate.
Rather than defend the Chattahoochee he would wait until Sherman crossed PeachtreeCreek, then attack while the army was split in two.
Additional notes: During the battle General Sherman's headquarters were at the Augustus Hurt (Howard) House (present-day Carter Center) while General Hood stayed at the Windsor Smith House (present-day Oakland Cemetery).
On July 20, during the battle, men under the command of Captain Francis Degress climbed to the top of a hill along The Decatur Road (now Dekalb Avenue) and fired the first artillery shells to land within the city limits of Atlanta.
Historically, Atlanta grew up on a site occupied by the Creek people, and the "peachtree" street was, in fact, not named for a peach tree of any sort, but for a large Creek settlement called Standing Pitch Tree after a tall lone tree.
Reportedly, the Creek used trees with fresh pitch (the sap of a pine tree) for solemnizing vows and treaties.
Urban legend states that Peachtree Street is atop a ridge which is part of the Eastern Continental Divide.