The Caterpillar Tractor Company was incorporated in 1925, but they were essentially selling rebaged equipment made by companies Holt and Best until 1927 when they created the "Model Twenty." A total of 8,201 were built to this spec through 1931.
If you want to really nerd out about this and other cool CATs (zing) you should check out By Eric C. Orlemann
Image: Caterpillar