Although it wasn't the first luxury car, the S-Class was truly revolutionary for many other reasons.
There are luxury cars and then there are luxury cars. Limousines have been around almost as long as the internal combustion engine, and the Grand Touring model is a concept even older than cars. But the big German luxury sedans which we see far more frequently than anything driven by a chauffeur are a much more recent invention. This is not to say that luxury sedans didn't exist before 1973, but when the Mercedes S-Class debuted that year, it created its own subgenre of luxury sedans.
These are cars which are not limos, but still manage to set themselves apart from cars where bigness is the primary indicator that it's supposed to be a luxury car. The S-Class was obviously not the first big non-limo Mercedes sedan, but it did show a change of focus on the part of Mercedes-Benz. The name alone tells you quite a bit, S-Class is an abbreviation of "Sonderklasse", which means "special class". These were cars which received special attention from designers and engineers, and were to take the role of standard bearer for Mercedes away from the old 600 limousines.
The 600s were excellent cars, but they proved to be a bit huge and ostentatious for many people. What were you to do if you had a lot of money but weren't a head of state? The first true S-Class was the W116. This was the latest in a line of cars dating back to 1954, but it was the first to be given the name S-Class, and when the W116 replaced the W108/W109 in 1973, it showed a significant change in the attitude which Mercedes had toward the car. This started with safety features, the new S-Class offered a level of safety technology previously unheard of in this segment.
The S-Class and its competitors remain some of the safest vehicles on the road, no matter what certain Swedish companies might tell you. On the first S-Class, these included significant improvements in the area of the windshield and windshield wipers, which combined to provide excellent visibility in the rain. Surfaces on the interior were padded in places where passengers were likely to get thrown into during a crash. The taillights were designed to be more resistant to caked mud, the car's first aid kit was moved to make it more accessible and the bodywork was even more rounded as a passive pedestrian safety feature.
In fact, the W116 S-Class would be one of the first cars to be fitted with ABS and airbags. The body structure was strengthened to protect occupants as well, and the gas tank was moved from the very back to above the rear axle to reduce the chances of it being ruptured in a crash. A self-leveling hydropneumatic suspension system was included as both a technological achievement and a luxury feature. Mercedes offered a surprising range of engines for the W116, including a 3.0-liter five-cylinder diesel which was one the first automotive diesel engines to be turbocharged.
Four different gasoline engines were offered as well, including the legendary 6.9-liter V8, the biggest engine to have been put into any postwar Mercedes-Benz up to that point. It was named European Car of the Year in 1974, and the S-Class has since become the best-selling luxury flagship sedan on the market. Competition for this title comes primarily from BMW and Audi. It's important to note the BMW 7-Series debuted in 1977, just a few years after the S-Class and once BMW fully understood the value of having such a vehicle in their lineup. Audi followed in 1988 with the V8, the car which would evolve into the A8.
But neither of these would quite reach the level of prestige of the S-Class. The original flagship luxury sedan is still considered by many to be the car which defines the genre. When Toyota decided to launch the a new luxury brand with the Lexus LS in 1989, the car was so obviously aimed directly at the S-Class that many have wondered why Mercedes never sued over the similarity of the design. Groundbreaking as the first S-Class had been, the competition from the Lexus LS caused Mercedes to step up their game with the S-Class in the early Nineties.
The car became still more luxurious, a V12 engine was offered, and even more safety features were introduced. Eventually, this put the technology, luxury and price of the S-Class out of reach of competition from Lexus and Infiniti, once again leaving just the 7-Series and A8 as competition. The S-Class was most certainly not the first luxury sedan, but what it did was bridge the gap between the super luxury cars produced by companies like Rolls-Royce and the more mainstream luxury cars. Long-wheelbase models even made some big limos obsolete. The S-Class was successful because it made us rethink what we wanted from a luxury car.