Unit Rig was a manufacturer of haul trucks, sold under the brand name Lectra Haul. Unit Rig was founded in 1935 by Hugh S. Chancey and two partners, Jerry R. Underwood and William C. Guier, who formed a partnership to build a rotary drill rig for oil field work that was more mobile than existing designs. The group based the company in Tulsa, Oklahoma. By 1947, the partnership between the men was beginning to break down when Underwood died, leaving Chancey and Guier as the remaining partners. Guier eventually took control of Unit Rig and in 1951 sold it to Kenneth W. Davis, who already had several oil-field related businesses under the parent company name of Kendavis Industries International. During the 1950s, Unit Rig began to diversify its products away from the limited oil-field products and looked towards mining products to utilize their manufacturing facilities. R. G. LeTourneau had already adapted compact electric drive wheels to construction machinery with great success, prompting Unit Rig to investigate the possibility of building a truck and finding a suitable client to take the finished machine.