At first, trains pulled by steam locomotive carried freight only. In 1825 the Stockton and Darlington Railway in England started to operate regular services for passengers. From that time until mid-20th century, the steam locomotive was the dominant form of train power. Today almost all modern trains are powered by locomotives with diesel,  electric or diesel-electric engine (seldom by gas turbines). The steam locomotives are used only for special purposes (see Puffing Billy-Steam Engine Trains).