This paper reviews the milestones achieved with cryogenic liquid propellant rocket engines, discusses current technology improvement programs, and projects future engine designs. During the last two decades, these cryogenic rocket engines have played a major role in rocketry and achieved numerous important milestones. These engines power the Vanguard, Redstone, Thor, Atlas, and Titan I vehicles , the Saturn I and Uprated Saturn I vehicles, and will soon be employed in the Saturn V for the Apollo missions. The requirements dictated by these vehicles have necessitated growth from the 27,000-pound-thrust Vanguard engine to the 7,600,000-pound-thrust booster cluster for the Saturn V. Gains in specific impulse have also been significant. The successful application of liquid hydrogen in the Centaur and Saturn upper-stage rocket engines was a major achievement.