The term ‘bay window’ covers any type of protruding window, regardless of its shape or whether it appears on one or more floor of a building. The earliest bay windows date back to the Renaissance and were typical of palaces and great houses of the period. Invariably, these bay window were rounded, extended over a series of floors and often topped with domes.
Bay windows became particularly popular in the Victorian era with canted or angled bays the most common form in the mid-19th century. Flatter, squarer bays became popular at the turn of the century. They were introduced to terraces and rows of urban houses to increase the amount of light in a confined area without taking up too much additional space. They also greatly improved the aesthetic of a row of houses with otherwise flat facades.