Prior to 1930, what wiring method was commonly used in U.S. homes?

Knob-and-tube wiring was widely used in U.S. homes prior to 1930 due to its simplicity and effectiveness at the time. This method involves running individual conductors through knobs (ceramic insulators) and tubes (for protection against physical damage) to protect wiring as it ran through walls and ceilings. It was particularly popular because of how it allowed for easy installation in wooden structures, common in that era.

This method also has historical significance, as it represents the transition from older wiring techniques to more modern safety standards that evolved later in the 20th century. In contrast, options like Romex wiring and non-metallic sheathed cable became prevalent only after World War II, and metal conduit wiring, while used in industrial applications, was not the standard method for residential homes before 1930. Understanding the historical context of electrical wiring methods provides insight into the safety and building codes that evolved to address issues related to earlier forms of wiring like knob-and-tube.