Inventions of the 1920s
The "Roaring Twenties", as the decade of 1920 is known, was one of the most optimistic and boisterous period of time for many Americans.

The World War I had come to an end, and due to the boom in the consumer-goods industry, new products were available to Americans. The period was also a time of inventions and discoveries, and many new gadgets and appliances came into being in this decade.
Eskimo Pie (1920)
eskimo pie
Inventor: Christian Nelson

The popular Eskimo Pie ice cream was first manufactured by Christian Nelson in 1920, a chocolate-covered vanilla ice cream wrapped in a foil. It is believed that Nelson got the idea for Eskimo Pie when he saw an indecisive boy thinking whether to go for a chocolate, or an ice cream. Nelson teamed up with Russell Stover to produce the Pie on a massive scale, and the duo achieved considerable profit from its sales. Today, Eskimo Pie is marketed in USA by Nestlé.
Jungle Gym (1920)
jungle gym
Inventor: Sebastian Hinton

Sebastian Hinton, a lawyer from Chicago, invented the first jungle gym in the year 1920. It was very popular amongst kids. Jungle gyms were also known by the names of monkey bars and climbing frames.
Radio/TV Transmission (1920)
radio transmission
Inventor: Ernst Alexanderson

Before 1920, radio transmission consisted of a series of dots and dashes, transmitted by inefficient machines. The credit for inventing goes to. After rigorous experimentation and hard work, Ernst Alexanderson, a Swedish-American engineer invented a high-frequency alternator (a fore-runner to the present-day radio/television transmission) with which transmission of radio waves became successful.
A few years later, he developed a scanning disk and high-frequency neon lamp for television transmission.
Traffic Lights (1920)
traffic lights
Inventor: William Potts

William Potts, a police officer from Detroit, Michigan, invented the traffic lights. He made his invention by using red, green and amber lights, and wire. The traffic lights were installed for the first time in the region of Woodward and Michigan Avenues in Detroit, United States.
Band-Aid (1920)
band aid
Inventor: Earle Dickson

Earle Dickson made Band-Aid to tend to the injuries of his wife, who often cut herself while doing household chores. Earle Dickson worked in the company, Johnson & Johnson, that manufactured gauze and tape. He used a piece of tape with a small-sized gauze in the middle, and put it on his wife's injured hand. He told the idea to his boss, James Wood Johnson, who instantly liked it and put Band-Aid into production.
In 1924, Johnson & Johnson produced Band-Aid on a massive scale and made Earle Dickson the Vice-President of the company.
Hair Dryer (1920)
hair dryer
Inventor: Ambiguous

Prior to the 1920s, women used to blow-dry their hair by inserting a flexible pipe in the exhaust of a vacuum cleaner. In 1920, the first hair dryer was invented. Though the machine was not efficient enough and got overheated easily, it was, of course, better than using a vacuum cleaner!
Headrest (1921)
Inventor: Benjamin Katz

Invented by Benjamin Katz in 1921, headrests attained widespread popularity due to the comfort they provided to automobile users. The National Highway Traffic Safety Administration (NHTSA) mandated the use of headrests in all new cars sold on or after January 1st, 1969.
Lie Detector (1921)
lie detector
Inventor: John A. Larson

Lie detector, or polygraph was invented by John A. Larson, a medical student, in California. The device measured the heartbeats and breathing rate of a person in order to check whether the person was lying or not. If the pulse rate and breathing were high, then an alarm would buzz, indicating that the person was lying.
Flow Process Chart (1921)
flow chart
Inventor: Frank Gilbreth

Flow process chart was made by scientist Frank Gilbreth in 1921 as a presentation to American Society of Mechanical Engineers (ASME). A flow process chart is a diagram that depicts the step-by-step working of a program. Flow process chart was further developed by Allan H. Mogensen.
Convertible (1922)
convertible car
Inventor: Ben P. Ellerbeck

Although there have been numerous modifications and developments to the design of convertibles, the credit for envisioning and making the first practical retractable manual hardtop system goes to Ben P. Ellerbeck in 1922. The first power-operated retractable hardtop was made by a Parisian Georges Paulin in 1934.
Water Skiing (1922)
Inventor: Ralph Samuelson

The Roaring Twenties gave us one of our favorite adventure sports, water skiing. Invented by Ralph Samuelson in 1922, water skiing has developed into a major beach sporting event. It is reported that Samuelson experimented with water skiing for the first time by using a pair of boards and a clothesline. Samuelson also taught water skiing to aspiring water skiers.
Radial Arm Saw (1922)
arm saw
Inventor: Raymond DeWalt

Raymond DeWalt invented the first radial arm saw in the year 1922, and it was patented in 1925. Radial arm saws were mostly used for cutting long pieces of lumber. Raymond sold his invention under the name of Wonder Worker and made a considerable profit out of it.
Audiometer (1922)
Inventor: Dr. Harvey Fletcher

In the year 1922, American physicist, Dr. Harvey Fletcher invented the audiometer - a device which is used to measure and evaluate hearing loss. Since then, audiometers have been used widely, and today, they are a part of the standard equipment in clinics and hospitals treating hearing loss.
Bulldozer (1923)
Inventor(s): James Cummings & J. Earl McLeod

Bulldozer, one of the most efficient machines used in construction process, was invented in 1923 by a farmer, James Cummings, in collaboration with a draftsman named J. Earl McLeod. In the years following 1923, bulldozers were widely used to dig canals.
Cotton Swabs (1923)
cotton swabs
Inventor: Leo Gerstenzang

Cotton swab was invented by a Polish-born American, Leo Gerstenzang, in 1923. He sold his invention under the name of "Baby Gays", and it was later changed to "Q-Tips", with the Q standing for quality. Cotton swabs have been used mainly as ear-cleaners, but in the recent years, concerns have been raised about the risk these might pose to the eardrum.
Instant Camera (1923)
instant camera
Inventor: Samuel Shlafrock

An instant camera is capable of generating a developed film image. It consists of a camera and portable darkroom in the same compartment. Edwin Land invented the first commercial instant camera in 1948, but it is reported that the first instant camera was developed by Samuel Shlafrock in 1923.
Locking Pliers (1924)
locking pilers
Inventor: William Petersen

Locking pliers are also known as Mole grips or Vise-Grips. These can be locked into position, using an over-center action. Locking pliers were invented by William Petersen in De Witt, Nebraska in 1924. Thomas Coughtrie further developed the model and invented the Mole grips in 1955.
Cheeseburger (1924)
Inventor: Lionel Sternberger

There is some ambiguity on the year in which cheeseburgers were first made available to people. While some believe that Lionel Sternberger made the first cheeseburger in 1924, others claim that the year of invention was 1926. Over the years, cheeseburgers have undergone numerous transformations, and today, apart from cheese, they are served with lettuce, onion, pickles, mayonnaise, etc.
Earth Inductor Compass (1924)
earth inductor compass
Inventor: Morris Titterington

The earth inductor compass was invented by Morris Titterington in 1924. It was widely used in the aerospace industry and helped in determining the direction of the aircraft. Besides designing the earth inductor compass, Titterington also designed the bubble sextant, a device used to measure the angle between any two visible objects.
Gas Chamber (1924)
gas chamber
Inventor: State of Nevada

There is ambiguity over who exactly came up with the idea of carrying out a death sentence through a gas chamber, but many historians believe that it was the State of Nevada, which executed a convicted murderer through this method. Gas chambers gained notoriety during the Holocaust as the reigning Nazi government used it to put millions of Jews and political opponents to death.
Moviola (1924)
Inventor: Iwan Serrurier

Moviola was invented by Iwan Serrurier in 1924. It was an innovative device for the film industry as it allowed editors to watch and edit a film simultaneously. Initially made to be sold as a home movie projector, Moviola didn't make the desired profit for Iwan, and it was on the advice of an editor, that Iwan adapted the device to be used for film editing.
Radio Altimeter (1924)
radio altimeter
Inventor: Lloyd Espenschied

Radio altimeter is a device which measures the distance between the aircraft and the ground directly below it. When it was invented in 1924 by Lloyd Espenschied, it was thought to be a groundbreaking invention as other devices could only measure the distance between the aircraft and a predefined sea-level. However, it wasn't until 1938 that Lloyd's idea and design was put to form by Bell Labs.
Masking Tape (1925)
masking tape
Inventor: Richard Drew

Historians believe that the idea of inventing a masking tape came to 3M employee, Richard Drew, when he observed the difficulty faced by workers while painting cars. The adhesive that they used, often stuck to the surface when removed, and they had to redo the whole thing. Drew worked on the concept of having a tape that has a gentler adhesive so that the tape doesn't damage the area upon which it is applied. Drew received the patent for masking tape in the year 1930.
Tilt-A-Whirl (1926)
Inventor: Herbert Sellner

In the year 1926, Tilt-A-Whirl was operated at an amusement park in Minnesota. Its inventor, Herbert Sellner, had spent years building it, and once it was completed, it became an instant hit among people, notably for making riders experience nausea.
Power Steering (1926)
power steering
Inventor: Francis W. Davis

Although numerous inventors had tried to build a fully-functional power steering system, it was Francis W. Davis, who invented the first practical power steering system. However, due to cost factors, major automakers of that time didn't include power steering in their vehicles. The technology was widely accepted in 1950s, and today, it is a standard for modern vehicles.
Drive-Through (1926)
Inventor: City Center Bank

Drive-throughs are ubiquitous these days, but it was in the year 1926, that the world got to see them for the first time. City Center Bank is credited for being the first bank to open a drive-through window. Burger outlets and restaurants soon followed suit and drive-throughs became commonplace.
Liquid-Fueled Rocket (1926)
liquid fueled rocket
Inventor: Robert Hutchings Goddard

The first liquid-fueled rocket was launched by Robert Hutchings Goddard of the United States. During the first World War, he developed liquid-fuel rockets for use in armed weapons. His pioneering work in the field was evident from the fact that he possessed 214 patents in rocketry.
Pop-up Toaster (1926)
Inventor: Charles Perkins Strite

Charles Perkins Strite invented the pop-up bread toaster in 1919, and received a patent for it on October 18, 1920. Pop-up toaster was a big development over the semi-automatic toaster as it was able to eject the slice of bread/toast after toasting it. Waters-Genter Company worked on the invention of Charles, and came out with the first consumer pop-up toaster - Toastmaster - in 1926.
It could simultaneously toast both sides of the bread, and turn itself off automatically after making the toast. The pop-up toaster was quite an innovation in the 1920s, saving considerable amount of time for thousands of working-class people.
Jukebox (1927)
Inventor: The Automatic Music Instrument Company

1920s also gave the world its first jukebox. The Automatic Music Instrument Company built the first automated instrument and it gained popularity as jukebox in the 1930s.
Garbage Disposal (1927)
Inventor: John W. Hammes

Garbage disposals began to be used widely in 1940s, but the idea and the inspiration for the world's first garbage disposal had come to John W. Hammes in 1927. It was used between the sink of the kitchen and drain, and its primary use was to mesh waste food, so that it doesn't block any drainage pipes. Although garbage disposals were well-received in the US, their use remains limited around the world.
Pressure Washer (1927)
pressure washer
Inventor: Frank Ofeldt

Pressure washer was invented by Frank Ofeldt in 1927. It was very useful for people working in the construction industry as it made it easy to clean paint, grime, dust, etc., from buildings. It also found its use in car washing sector.
Recliner (1928)
Inventor(s): Edward Knabusch and Edwin Shoemaker

The comfort of a recliner was first experienced by people in 1928. It was invented by Edward Knabusch and Edwin Shoemaker in Monroe, Michigan. Their recliner was completely made of wood. Leather padded recliners were later developed and made available to consumers.
Ice Cube Tray (1928)
ice tray
Inventor: Lloyd Groff Copeman

Ice cube tray was invented by Lloyd Groff Copeman in 1928. Soon after their invention, ice cube trays became a household name and were preferred over crushed ice. The use of ice cubes in drinks created the popular phrase, "On the rocks."
Bubble Gum (1928)
bubble gum
Inventor: Walter Diemer

Bubble gum, or bubblegum, was invented by an accountant, Walter Diemer. The bubble gum was marketed under the brand name "Dubble Bubble", and according to estimates, its sales exceeded $1.5 million in its first year.
Bow Tie (1928)
bow tie
Inventor: Ambiguous

Bow tie, or clip-on tie, was first seen in the market in the year 1928. It is not clear as to who invented it, but these ties were first sold in Clinton, Iowa, USA. It was a major hit among policemen and people who weren't comfortable with the idea of having a knot on their neck as it made them vulnerable while handling violent offenders.
Electric Razor (1928)
Inventor: Colonel Jacob Schick

The first electric razor was invented by Colonel Jacob Schick in the year 1928. It was a revolutionary invention of that time, and was well-received in the market. As one could shave quickly without using soap, or water, electric razors grew in demand quickly.
Negative Pressure Ventilator (1928)
iron lung
Inventor: Phillip Drinker & Louis Shaw

Negative pressure ventilator, or iron lung, as it is informally known, was invented by Phillip Drinker and Louis Shaw in 1928. The device gained widespread admiration in the same year, when an eight-year old girl was saved by putting her on the iron lung. After its invention, it was mainly used as a substitute for people with respiratory problems, caused due to poliomyelitis.
Penicillin (1928)
Inventor: Sir Alexander Fleming

Penicillin, one of the widely used antibiotics, was invented by scientist Sir Alexander Fleming after studying bacteria. Since penicillin was not approved by the FDA, it was not popular in those times. Subsequent research studies had been done about the effects of penicillin on various strains of bacteria. It was only after the World War I that people started using penicillin as a life-saving drug.
Frozen Food (1929)
frozen food
Inventor: Clarence Birdseye

Clarence Birdseye, a naturalist from the United States, invented frozen food. In New York, he started a packing company called Birdseye Seafoods, Inc., in 1924. He introduced a system wherein dressed meat and vegetables were preserved in waxed-cardboard cartons, after being exposed to high pressure. In 1930, he succeeded in patenting the Birdseye system of freezing food.
Tampon (1929)
Inventor: Dr. Haas

Tampon is a material that is used to absorb fluids emanating out of a wound or cavity. Although devices similar to tampon had been made earlier as well, but it was for the first time in 1929 that an applicator was also used with the device. The device was made by Dr. Haas, and was sold under the name Tampax.
Sunglasses (1929)
Inventor: Sam Foster

Sunglasses were used by Chinese judges in the fifteenth century, but their intention wasn't to protect their eyes from the glare of the sun. They wore tinted sunglasses to maintain a poker face in the courts. Sunglasses became a rage in 1929, when Sam Foster, founder of the Foster Grant Company, began mass-producing them in Atlantic City, New Jersey.
In the 1930s, sunglasses were used extensively by pilots and the legendary company, Ray Ban, brought polarized sunglasses to the world.
The 1920s was truly a decade of inventions and technological advancement. The number of inventions made in this decade is a testimony to the effort of scientists and inventors of that era. Besides creating new products, inventors also put in consistent efforts to better the existing technology, most notable being the advancement made in the field of automobile engine. Henry Ford's Model T, launched in 1920, had made every American dream about owning a car, and this hysteria gave a fillip to the efforts of scientists involved in improving the performance of the internal combustion engine. A number of patents were registered in the 1920s, and in the year 1925, a Swedish engineer, Jonas Hesselman invented a spark-ignition engine that worked on direct gasoline injection.
Advancements were also made in the field of consumer-appliances. In 1926, John Logie Baird gave the first demonstration of televised moving images, which provided the foundation for the invention of all-electronic-television. Numerous research works were started in the 1920s, which helped in the creation of new technology in the later decades. Besides the advancement in science and technology, the decade of 1920s is also remembered for the effect it had on the popular culture through films, art, and literature.