In 1962, the U.S. Navy, U.S. Coast Guard and U.S. Marine Corps versions were all redesignated as H-19s like their U.S. Army and U.S. Air Force counterparts.

The H-19 pioneered the use of a nose-mounted radial engine powering a single fully articulated main rotor located above the cabin, which helped maintain a proper center of gravity under varying loading conditions without requiring ballast to maintain longitudinal stability as with prior Sikorsky designs.

[1] The first customer was the United States Air Force, which ordered five YH-19 aircraft for evaluation; the YH-19's first flight was on 10 November 1949, less than a year after the program start date.

An additional 447 were manufactured by licensees of the helicopter including Westland Aircraft, SNCASE in France and Mitsubishi in Japan.

[1] The helicopter was widely exported, used by many other nations, including Portugal, Greece, Israel, Chile, South Africa, Denmark and Turkey.

[1] The impetus for this design choice was the recent rejection of the Sikorsky XHJS by the U.S. Navy in favor of the tandem rotor Piasecki HUP Retriever; the Navy had strongly objected to the necessity to use ballast in the cabin-forward XHJS to maintain proper weight and balance, prompting Sikorsky to seek single-rotor design alternatives that did not require this.

[1] The YH-19 prototypes featured a blunt aft fuselage and a single starboard-mounted horizontal tailplane with a small vertical fin at its outboard end.

Initial production models added a large fillet-like fin behind the fuselage and under the tailboom, and the tailplane configuration was changed to an inverted "V" shape.

[3] Early H-19 and HO4S variants were powered by a Pratt & Whitney R-1340-57 radial rated at 600 hp (450 kW) and used a centrifugal clutch that automatically engaged the main rotor when a preset engine speed was reached.

Undergoing tests such as medical evacuation, tactical control and frontline cargo support, the helicopter succeeded admirably in surpassing the capabilities of the H-5 Dragonfly which had been used throughout the war by the Army.

Their performance continued to improve and in Operation Haylift II on 23–27 February 1953, HMR-161 lifted 1.6 million pounds (730 t) of cargo to resupply two regiments.

[4] The success of helicopter operations with the USMC prompted the service to seek a military light utility vehicle that the HRS could lift, leading to the development of the aluminum-bodied, 1,700 lb (770 kg) M422 Mighty Mite in the early 1950s.

H-19 pilots Joe Sullivan and Don Crabb, alerted that two damaged Sabres were headed towards them, saw McConnell's F-86 and changed course to parallel it.

Historian Kenneth P. Werrell writes that the misleading, staged photo was likely a ruse to conceal the fact that the H-19 was not originally on an air rescue mission but was instead supporting special operations in the Cho-do area.

[7] On 1 September 1953, Sabena used the S-55 to inaugurate the first commercial helicopter service in Europe, with routes between Rotterdam and Maastricht in the Netherlands and Cologne and Bonn in West Germany.

Piasecki H-21 and Sud-built Sikorsky H-34 helicopters rapidly displaced fixed-wing aircraft for the transport of paras and quick-reaction commando teams.

[12] In the mid-1980s, the U.S. Army sought an economical helicopter to simulate the sound and radar signature of the Soviet Mil Mi-24 during exercises.

The aircraft were also outfitted with special intake and exhaust silencers, carbon fiber noise-absorbing engine compartment doors, and a transparent Plexiglas floor.