The crawler uses a laser guidance system and a leveling system to keep the Mobile Launcher Platform level within 10 minutes of arc (0.16 degrees about 30 cm (1 ft) at the top of the Saturn V), while moving up the 5 percent grade to the launch site. The height from ground level to the platform is adjustable from 6.1 to 7.9 m (20 to 26 ft), and each side can be raised and lowered independently of the other. The vehicle measures 40 by 35 meters (131 by 114 ft). Each track has 57 shoes, and each shoe weighs 900 kg (1,984 lb). The crawler-transporter has a mass of 2,721 tonnes (6 million pounds 2,999 short tons) and has eight tracks, two on each corner. The two crawler-transporters were added to the National Register of Historic Places on January 21, 2000. While other vehicles such as bucket-wheel excavators like Bagger 293, dragline excavators like Big Muskie and power shovels like The Captain are significantly larger, they are powered by external sources. Upon its construction, the crawler-transporter became the largest self-powered land vehicle in the world. The two crawler-transporters were designed and built by Marion Power Shovel Company using components designed and built by Rockwell International at a cost of US$14 million each.
The crawler-transporters carry vehicles on the mobile launcher platforms used by NASA, and after each launch return to the pad to take the platform back to the VAB.
They were then used to transport Space Shuttles from 1981 to 2011. They were originally used to transport the Saturn IB and Saturn V rockets during the Apollo, Skylab and Apollo–Soyuz programs. The crawler-transporters, formally known as the Missile Crawler Transporter Facilities, are a pair of tracked vehicles used to transport spacecraft from NASA's Vehicle Assembly Building (VAB) along the Crawlerway to Launch Complex 39.