NASA was keenly aware that their plans for the Saturn family of rockets would result in much more powerful boosters that would require larger and more complex launch facilities. Launch Complex 34 was formally dedicated on June 5th, 1961, and was for a time the largest such facility in the free world. The first launch, SA-1, was set for October of 1961. A total of four Saturn 1 and three Saturn IB boosters were launched there. The devastating Apollo 1 fire happened at LC34. More than two years later, the launch pad was used for the Apollo 7 mission. After that, the complex was decommissioned. Today, the launch platform is all that remains, and is home to a memorial to the Apollo 1 astronauts.
As construction of Launch Complex 34 got underway, a study revealed that a Saturn explosion would render the site unusable for at least a year. So plans were drawn up and approved for a second Saturn launch site, designated Launch Complex 37. Pad A was never used. The first launch from Pad B was a Saturn I on January 29, 1964. Over the course of the next four years, five more Saturn I and two Saturn IB boosters were launch from Pad A, which was decommissioned in 1972.
To handle the full Saturn V, NASA commissioned Launch Complex 39. The original design was to build five pads, connected to the Vehicle Assembly Building by the Crawlerway. In the end, only two pads were built for Apollo, designated 39A and 39B. The first launch of the Saturn V from Pad A occurred on November 9, 1967. It carried the unmanned Apollo 4 space capsule. In total, thirteen Saturn Vs and four Saturn IB boosters were launched from Pad’s A and B. The final launches carried the crews of the three Skylab missions and the astronauts who rendezvoused with the Soviet cosmonauts during the Apollo-Soyuz mission in July, 1975.
After Apollo, Launch Complex 39 was used by the Space Shuttle. It remains in operation. 39A is used by SpaceX. 39B was reconfigured for use by the Space Launch System. 39C was added in 2015 to handle smaller rockets. Launch Complex 37 was recommissioned in 2001 for United Launch Alliance missions involving the Delta IV rocket.