The Cambridge Companion to the Guitar

Instruments with plucked strings are of great antiquity and have been played in all countries where dance and songs were common forms of entertainment. The guitar is only one of them, but it became extremely popular as a portable instrument capable of producing harmonies. In its more or less recognisable present form it was developed in the fifteenth century in Spain, and during the immediately following colonial period, was diffused by European explorers, traders and missionaries throughout the world.

Its popularity during the nineteenth century, and especially during the twentieth, owes much to its adaptability for all sorts of performers...