Built in 1965, The crawlers carried the weight of the massive Saturn V rocket and Apollo capsule attached to the mobile launcher along with the launch umbilical tower (12.3 million pounds), and the space shuttle with solid rocket boosters and external fuel tank on top of the mobile launcher platform (11 million pounds) 131 by 114 ft

The crawlers are now being modified to carry NASA's Space Launch System (SLS) with the Orion spacecraft