The first cars and trains were steam powered. In 1906, a steam powered sports car set the land speed record at 126 mph. Most of the early massive trains until the mid twentieth century were steam powered. Heck, the Germans were even experimenting with a steam powered Messerchmidt with a coal furnace in the late stages of World War II. However, I have not been able to find anything on early steam powered tanks from World War I through the 1920s, 1930s, etc. What makes steam a poor choice for tanks?