The First Successful Crawler Tractor

Soft soil led to the development of a tracked tractor to maintain traction without sinking.

This 1913 Holt 60 illustrates the original front steering design.
This 1913 Holt 60 illustrates the original front steering design.

At the turn of the last century, Benjamin Holt of Stockton, CA, was a leading manufacturer of steam traction engines. These machines operated on the same principle as a steam locomotive, with a boiler providing steam to engines that powered the wheels upon which it traveled. These machines were used in a wide variety of applications, including construction, logging, heavy overland hauling and agriculture.

A traction engine had to combine weight and firm traction in order to do its work most efficiently, and the largest traction engines were quite impressive in the effort to optimize both forces. On firm, stable ground, this was no problem. But they encountered a difficulty in the Sacramento-San Joaquin River Delta west of Stockton.

Much of the land in the Delta consisted of marshy islands that had been reclaimed for farming. The resulting peat soil was wonderfully fertile, but too soft for the traction engines. The considerable weight necessary to work agricultural implements caused them to sink in. Modifying them with larger and/or wider wheels gave them better flotation, but they tended to lose traction; and the added weight offset somewhat the improved flotation. A smaller traction engine would be less prone to sink, but would not be sufficiently powerful.

In 1904, Holt solved this problem by building what led to the first commercially successful crawler tractor. Other inventors were also developing crawlers, but Holt’s was the idea that lasted. The logic of the design was that a gas-powered machine weighed less than steam, in addition to all its other operating advantages over steam, and mounting it on a pair of continuous, cleated steel belts gave it the necessary flotation and traction. There was no means of steering through the crawlers at the time, so it was equipped with a front steering wheel. Holt’s crawler tractor entered production in 1906.

Watching Holt’s prototype at work, a photographer commented to Holt that its motions reminded him of a caterpillar walking. The comment inspired Holt to trademark the caterpillar name, and the 1925 merger between Holt Manufacturing Company and C. L. Best Tractor Company formed Caterpillar Tractor Company.