The obvious thing you would answer would be the wheel, well that was the Stone Age, around 3500 BC
Or would you guess the tire, you are getting closer.
In 1839 Charles Goodyear was credited with the discovery of the vulcanization process. Vulcanization is the process of heating rubber with sulfur. This transforms sticky raw rubber to firm pliable material which makes rubber a perfect material for tires.
The story of Charles Goodyear is a sad one. Although he dedicated his entire life to making rubber a better form, he would never profit from all his work. Charles Goodyear died bankrupt.
How about something a lot simpler? The twist grip, it is debatable that Roper steam velocipede
had the first twist grip, where in fact it had a handlebar that rotated completely not just a sleeve rotating…but the idea was born and it is credited with the first use of a similar mechanism still in use today.
Glenn Curtiss, unlikely to have been aware of the prior uses of the twist grip, used it in his 1904 motorcycle land-speed record machine, and is sometimes credited as the inventor of the device. A man known for unique inventions from his small shop. His first motorcycle’s carburetor was adapted from a tomato soup can containing a gauze screen to pull the gasoline up by capillary action.
In 1904 Indian Motorcycles claimed in their advertisements, for their 1904 models, to have invented the twist grip. Whether Curtiss, Gottlieb Daimler, or Roper, were the true inventors, is up for debate to this day.
What Indian Motorcycles can claim is, in 1904 Indian would have the earliest use of the device on a production motorcycle and still use it to this day…and they put a patent on it just to be sure. US Patent 765138