EARLY - Mid 20th Century
This era, as it's name suggests, lasted from about 1900 to 1950. However, this was also the era of MAJOR technological advances due to human's inane desire to fiddle with things. This resulted in the airplane, the tank, the atomic bomb, the computer, the calculator, the jet engine, the rocket engine, and many more. Most of the inventions during this era were either accidents that happened while trying to develop something else, or a result of the World Wars.