Why did windows in England have small squares, and when did it change?
Windows in England traditionally featured small square panes because, before the 19th century, glassmaking technology could not produce large sheets of clear, flat glass. Instead, glass was manufactured in small pieces and these were set into window frames with lead cames, resulting in the classic appearance of multiple small squares or rectangles within a single window.
This style began to change in the early 19th century with advances in glass production techniques, such as cylinder and plate glass methods. By the mid to late 1800s, it became possible and more affordable to install larger panes of glass, leading to the gradual decline of the small-pane style in favour of windows with fewer, larger sections.
Some examples of Edwardian and Georgian layouts
Take a look at Georgian and Victorian Sash Windows