He served as a surgeon at Fort Sumter, South Carolina during the confederate bombardment in 1861. He transferred to the infantry early in the war and led a brigade at Cedar Mountain which routed a division that included Stonewall Jackson’s unit, though it was later driven back. He was severely wounded at Antietam and returned to action at Gettysburg, where his division drove the Confederates out of "the valley of Death" beside Little Round Top, with Crawford dramatically seizing the colors and leading from the front. Although this was a relatively minor engagement, Crawford tried for years to become officially acknowledged as the sole savior of Gettysburg, but without success. The preservation of the battlefield, however, is largely due to his efforts.