When Mike Mulligan and his steam shovel, Mary Ann, lose their jobs to the gasoline, electric, and diesel motor shovels, they go to a little country town where they find that one new job leads to another
Katy, a brave and untiring tractor, who pushes a bulldozer in the summer and a snowplow in the winter, makes it possible for the townspeople to do their jobs.
The amazing horse Calico is responsible for capturing a gang of bad men, finding and rounding up the stolen cattle, and seeing that the Christmas party is a success, even for the outlaws
Maybelle loves to carry people up and down the hilly streets of San Francisco, until the City Fathers decide that she should be taken out of service in the name of progress.