Electric guitars, first patented in 1937, use a pickup and amplifier that makes the instrument loud enough to be heard, while also enabling the manufacture of guitars with a solid block of wood without the need for a resonant chamber. Solid-body guitars began to dominate the guitar market during the 1960s and 1970s; being less prone to unwanted acoustic feedback. After its popularization, a wide array of electronic effects units became possible including reverb and distortion (or "overdrive").

Source: Wikipedia