The document discusses how the location of the British iron and steel industry changed over time due to changing inputs and energy sources: 1) Originally in the late 1700s, the industry was located near forests which provided wood for charcoal and iron ore. Rivers provided water power. 2) By 1800, coal replaced charcoal as the main energy source so factories were built near coal mines in places like Wales and Yorkshire. 3) By the 1950s, oil replaced coal. Mills moved to coastal sites like Port Talbot to import coal, iron ore, and oil by sea more easily.