Let’s start our story just after the straight razor was introduced…England in the late 1600’s. Prior to that time people used a number of fairly crude blades to accomplish what was probably a very uncomfortable shaving process. But after the straight razor arrived on the scene it quickly became the most popular shaving method. Some chose to shave their own faces but it takes time, patience and skill to handle the straight or “cut-throat” razor. So more commonly, a shaggy gentlemen would go down the street to their favorite barber to receive a shave.
The Concept
The first ‘safety razor’ was developed by Jean-Jacques Perret in the mid 1700’s. It was really just a straight razor with wooden guards that allowed only a small portion of the blade’s edge to protrude, similar to a woodworker’s plane. Perret was a brilliant craftsman who studied knifemaking and made surgical tools. And he was an absolute shaving luminary proved by his book La pogonotomie, ou L’art d’apprendre a se raser soi-meme or translated Pogonotomy, or The Art of Learning to Shave Oneself. Click through and take a look – I hope your French is more than passable.
The Shape
In 1847, William Henson invented and patented a T-shaped (or hoe-shaped) razor. It was a genuine departure from the standard straight razor since the blade was short and sat at a right angle to the handle. 
At the time, Henson was far more known for his improvements in lacemaking and aviation getting a patent on the Henson Aerial Steam Carriage.
This configuration change is elemental to our progress but we are still 50 years from the modern equivalent of today’s safety razor.
Almost there…
In 1880, the Kampfe Brothers patented the Star Safety Razor and that earns the distinction of being called the first safety razor. Unlike the modern razors to come, the original design still required removing the blade and stropping like a straight razor. Many additional patents followed from their subsequent companies as well as their competitors.
Jackpot!
It took the genius of King Camp Gillette in 1904 to put all the pieces together. His initial patent described a safety razor with the ability to replace the blades as needed. This was monumental since his high-quality, double-edged (DE) blades needed no stropping and no sharpening. The mechanical achievement in the razor itself was notable but the changes in the blades were significant for two reasons. 
First, Gillette’s blades were wonderfully made from thin sheets made of steel and sharpened on both sides. Second, the blades were the key to the whole business model because it gave Gillette and his company the ability to sell the needed replacement blades to an ever-growing market.
By 1915, Gillette was selling 450,000 razors and 70 million blades per year.
Its popularity grew through WWI as the US govt supplied the troops with Gillette safety razors and blades.
Evolution
Other razor designs were developed in that time and offered an alternative to the Gillette safety razor that was absolutely dominating the market. Schick was founded in 1926 but back then was called the Magazine Repeating Razor Company. They introduced a single-bladed safety razor system called an injector razor. When a replacement blade was needed, a magazine loaded with 20 blades was purchased. It allowed loading the new blades into the razor without handling the blade. Jacob Schick was a man with vision and he sold his company after only 2 years in order to work towards his next venture…the electric razor. Starting in the 1930’s, Schick successfully perfected his vision of the electric shaver and the Schick Dry Shaver company eventually became part of Norelco in the early 1980’s.
Many of these early injector razors still around and can be easily found on Etsy or ebay.
Cartridges and Disposables
Gillette continued its domination of the wet shaving market and the world had to wait until 1971 to see the next leap forward. The Trac II by Gillette was the first twin-blade shaving cartridge. These dual blade cartridges were purchased and released from the handle and replaced by sliding the new ones on.
Two blades was a big deal. Manufactures pushed the idea that after the first blade cuts, it lifts the hair up from the skin. Then the second blade would cut it at a lower point resulting in a better, closer shave.
In 1974, the French company Société Bic was already big in pens before they introduced the first disposable razor, a single blade encased in a plastic cartridge. It was yet to come to the United States but Gillette correctly recognized this threat and was not willing to lose any of his huge market share to this new competitor. Gillette quickly developed a razor that was essentially a Trac II cartridge fixed into a plastic handle. Gillette introduced this disposable, named the Good News, in 1976 and it hit the shelves before Bic’s razor reached the United States.
Disposable razors (both single use and replaceable cartridges) continued to grow in popularity and in 1977, Gillette was again the one to move things forward with the Atra razor. It was the first razor to feature a pivoting head and was hugely popular. The Sensor razor debuted about 12 years later and was the first razor to have spring-loaded blades.
Gillette continued to innovate and it all led up to the Mach3 razor in 1998. It was the culmination of years of research and hundreds of millions of dollars in development and marketing. The razor offered 3 good quality, spring loaded, coated blades in a newly designed, pivoting head. There were several versions of the Mach3 but in just six months it became the top-selling razor in North America and Europe.
Anyone of a certain age might remember the ads for the Mach3 razor. A fighter jet breaking through the sound barrier (Mach 1) then starting to fall apart as it approaches Mach 2. The jet achieves Mach 3 and the whole thing explodes and the razor goes flying into the hands of the shirtless pilot. Perhaps the millions of dollars was worth it since I still think of that ad fondly. The Mach3 is still a huge seller for Gillette.
Normal evolution or ridiculous…?
The march into the slightly outrageous continues. The Fusion razor by Gillette was released in 2006 and contained five thin blades. And from then until now the changes and “improvements” have overwhelmed the everyday shopper with more and more features, including more blades, vibrations, heat, precision trimmers and razor heads attached to pivoting balls. Why? Do all of these innovations really give you an easier or closer shave? Well…it is clear that these gadgets are definitely not the cheapest way to go.
However, this site has said the same thing many times…shaving is about personal preference. Dorco has a 7-bladed razor for sale or you can get heated razors with charging dock. If it is something you enjoy and satisfies your needs then stick with it!