I'm a member of our local historical society, and I often look through old pictures and negatives when I visit. Last night I came a cross this picture of a steam shovel excavating for a junior high school, which was dedicated in 1922. So this image was probably taken in 1921.
Before hydraulics, this equipment depended on chains, spockets, steel cables, and pulleys to do work. Even though they could work circles around manual and animal labor, these machines were slow, had limited motion, and couldn't handle very big payloads.
But diesel engines, hydraulics, and electronic controls have changed all that. Today's machines are much faster, more powerful, ergonomic, more controllable, and produce far less emissions. Still, you may sometimes hear people refer to these machines as steam shovels, even thoufgh steam hasn't been in wide use since early in the last century.