Looking at the coach wheels they were originally horse drawn ladders, so were likely used by being taken to the fire, then wheeled around by hand to get to a location then they were manually extended and were propped against the building wall.
they probably kept them when changing to trucks, and as the trucks were modernised these ladders stayed as part of the newer vehicles. I did see a NY fire dept video on YT where they had the ladder shop on display, and how some of the ladders they use are a century or more old and still in good condition and still in service.