Space Launch Complex 4 (SLC-4) is a launch site at Vandenberg Air Force Base, with two pads one of which is currently used by SpaceX to launch the Falcon 9 rocket. The complex was previously used by Atlas and Titan rockets between 1963 and 2005. It consisted of two separate launch pads, SLC-4W and SLC-4E, which were formerly designated PALC2-3 and PALC2-4 respectively. Both pads were originally built for use by Atlas-Agena rockets, but were later rebuilt to handle Titan rockets. The designation SLC-4 was applied at the time of the conversion to launch Titans.