These Alabama and Tennessee River rocks are what line the Crawlerway at the Kennedy Space Center. Every Space Shuttle mission (and formerly Apollo flights 8 through Apollo-Soyuz) has made the trip to Launch Pad 39 A or B by rolling down this track (known as Rollout), which is filled with several feet of rock and gravel to support the 18 million pound Shuttle stack, consisting of the Shuttle, Mobile Launch Platform and Crawler. They were obtained during the rollout of STS-114 on April 6, 2005.