The last attack of the battle of gettysburg is known as

Pickett's charge
This was an infantry assault ordered by confederate general  Lee against union General Maj. Gen. George G. Meade's Union positions on July 3, 1863, which was the last day of the Battle of Gettysburg.The battle resulted to a major victory for the union soldiers and after the battle,the confederate had lost both politically and militarily.