In response to huge domestic earth moving opportunities, Caterpillar introduced seven new scrapers in 1962.  Three of those were two-axle designs that remain the basis for their current product line-up.  This included the 651, which was upgraded to the 651B in 1968. At the time of its introduction, this machine was one of the most powerful and sophisticated single engine scrapers available.

Given the thousands of miles of interstate highway to be constructed and a growing population needing housing and infrastructure, the 651B was a perfect match to market needs.  These machines are huge (over 50 feet long and 14 feet high, with 550 hp to propel them), and with their newly developed power-shift transmission they set an unmatched bar for moving dirt.