COLUMBIA, S.C.—The Confederate flag is scheduled to come down Friday morning after more than half a century on the state Capitol grounds, lowered in a solemn ceremony and placed in a nearby museum.

A beaming Gov. Nikki Haley signed a historic bill Thursday, paving the way for the flag’s removal and capping a whirlwind push to take down a divisive symbol that has been a part of the state’s political landscape for decades.

“Today,...