Final answer:
The Battle of Gettysburg is considered the turning point of the Civil War, marked by the Confederate's strategic defeat and heavy casualties, preventing further invasions into Northern states.
Step-by-step explanation:
The three-day battle considered the turning point of the Civil War is the Battle of Gettysburg. This pivotal confrontation crippled the Confederacy to such an extent that Confederate troops were never again able to invade a Northern state. The Battle of Gettysburg took place from July 1 to July 3, 1863, became the largest and costliest battle ever fought in North America.
The battle concluded with a disastrous Confederate assault known as Pickett's Charge, resulting in heavy losses and a strategic defeat for General Lee's Army of Northern Virginia. Following Gettysburg, and the simultaneous Union victory at Vicksburg, the Confederacy's momentum was halted, marking a shift in favor of the Union in both the Eastern and Western theaters.