Fender Amplifiers have a long history. Leo Fender

Leo Fender

Clarence Leonidas "Leo" Fender was an American inventor who founded Fender Electric Instrument Manufacturing Company, or "Fender" for short...

 began building guitar amps before he started manufacturing guitars. The first of these amps were the K&F

K&F Manufacturing Corporation

K&F Manufacturing Corporation was a company started by Clayton Orr Kauffman and Leo Fender in 1945. K&F manufactured amplifiers and electric lap steel guitars. Very few of the K&F instruments have survived. The amps featured an 8" speaker with one input with a volume control or a 10" speaker with...

 models, which were produced between 1945 and 1946. The original Fender amps were tube-powered and the company also started producing solid-state models in the late 1960s.
The K&F amplifiers were the first "Fender" amps made.