By the end of WWI it had worked its way into country music and though it appears in other settings, these are the two types of music where it is most often heard.
Steel guitars are a small family of instruments closely related to the six string Spanish guitar.
To make this easier, the original steel guitar was held in the player's lap, and the electric ones are often referred to as a 'lap steel'. While the very first acoustic steel guitars had bodies much like the Spanish guitar, a special off-shoot of acoustic guitar, the resonator guitar first appeared in the 20's and is still popular today. Just to confuse matters more, Dobro makes instruments with both a 'Hawaiian' neck and a 'Rhythm' neck, although the term Dobro usually refers to an instrument meant to be played with a bar, and 'rhythm' neck refers to a Dobro with a fingerboard fretted like a standard guitar. Like the Spanish guitar, the steel guitar can be electrified. Since an acoustic body was no longer necessary and actually caused feedback problems, the steel guitar quickly acquired a solid body and became the first true lap steel.