The earliest electrified guitars

To understand what Les Paul achieved, it is important to transport yourself back to the early 1900's. Swing and Big Band music had replaced the earlier orchestras and were much louder, and the the guitarist was playing mostly rhythm and was in the background. As the bands became bigger, a purely non-amplified instrument could not be heard over the band. There were early attempts at creating an electrified guitar, most notably the Rickenbacker "Frying Pan." But there is a problem with a hollow bodied guitar. They all feed back because the hollow nature of the instrument causes it to resonate when amplified.
Les had experimented with hollow designs and had encountered this problem. Ever the tinkerer, he stuffed different things, even pouring plaster into a guitar to make it stop feeding back. It was in 1941 that he invented his first semihollow, called "The Log," at the Epiphone plant.

Giving Les Credit:
Now, some say that the earliest electric guitars were the Rickenbacker "Frying Pans" made from cast aluminum and tungsten pickups in 1931, but these were hollow bodied lap steels. But in 1928 at the age of 13 Les Paul applied a phonograph pickup to a Silvertone acoustic guitar he bought for $2.49, which makes him the earliest by 3 years!