NASA built two main launch pads during the Apollo program, 39A and 39B. The former was used for every Moon landing launch, except for Apollo 10, and most of the space shuttle missions. After the final space shuttle flight in 2011, NASA decided it needed just one of the pads for its future operations. So it leased Launch Complex 39A to SpaceX.
The company had intended to use Launch Complex 39A primarily for launches of its new Falcon Heavy rocket and commercial crew missions. However, on September 1, 2016, a static fire test accident at SpaceX's other Florida launch pad, Launch Complex 40, caused severe damage to facilities there (repairs may be complete later this summer, according to company president Gwynne Shotwell). This pushed SpaceX to expedite its refurbishment of Launch Complex 39A and to expand its use for all launches from the East Coast.
from Ars takes you to the pad a day before SpaceX’s historic launch