The Classic Era was a big change for some main manufacturing companies including John Deere and Oliver. During the 50s and 60s the John Deere line went from letters for models to numbers, they also went from tow-cylinder engines to four- and six-cylinder engines. John Deere also jumped to number one in tractor sales. Steel wheel tractors were becoming a thing of the past during the Classic Era. There were some significant changes to compact tractors in the 50s including the addition of the three-point hitch, along with the redesign allowing driver’s to enter the tractor from the side.