PEORIA Ill -- The prototype of Caterpillar's first mass produced diesel engine from 1931 arrived at the museum today.
This 3,500 pound engine traveled all the way from the Smithsonian's Hall of Machinery in Washington D.C., where it was kept for 30 years.
Due to the lack of room, the engine was put into storage at the Smithsonian, and now it has made it's debut in Peoria.
Museum Officials say they are excited to add the new display to "The Street" gallery.
"It's huge. In our history gallery, "The Street", the scenario or story that we are telling is the story of innovation or entrepreneurship and so to not have Old Betsy not being part of that story would be a loss for all of us. So we are so pleased she is back," said Senior Vice President of Programs, Kate Schureman.
Old Betsy is painted gray, in her originally developed color from 1931.
Officials say the prototype was painted "Caterpillar yellow" at one time but is back to it's original state.