Most of the first motorcycles made were basically bicycles with an internal combustion engine strapped on somehow. These bikes were constructed just as "roads" were beginning to appear, so they were built to ride off road as well. Therefore, even the first motorcycles could be referred to as "dirt bikes". So dirt bikes (and street bikes) have been around since the dawn of motorycling, just at the time they were simply considered regular motorcycles.
Honda
the first dirt-bike ever made was a honda. There were bike manufatures in Europe that were making dirt type bikes before Honda was even a company.
Yamaha did....
Yamaha made the first Yamaha dirt bike
DJL made the first dirt bike.
KTM
He made the first dirt bike
Dirtbikes are made everyday in Japan..........
Travis Campa in 1863.
harley Davidson
The PW50 is a dirt bike that is manufactured by Yamaha. It is branded as "The first choice for first timers." as it is made to be used by children rather than adults.
It's made out of dirt obviously hence the name dirt bike.