Caterpillar founders C.L. Best and Benjamin Holt started out as competitors in the mid-1800s. Both men had multiple inventions to their names, but most significantly, Holt invented a steam tractor while C.L. Best created the track-type tractor, which allowed heavy steam tractors like Holt's to prepare agricultural fields without getting stuck in soggy soil. In 1925, the two men decided to merge their companies to create the Caterpillar Tractor Co. That first year, Caterpillar adopted a red wavy "Caterpillar" logo. The first new product they produced was called the Twenty Track-Type Tractor. Interestingly, all Caterpillar machines were originally painted battleship gray, but in 1931, the company switched to using Hi-Way Yellow with black trim. In 1931, Caterpillar began pushing for the use of diesel fuel and released its first diesel-powered machine, the Caterpillar Diesel Sixty Tractor. Caterpillar also began designing its own diesel engines; this resulted in diesel replacing gasoline as the main fuel source in heavy-duty equipment. During World War II, Caterpillar manufactured roughly 51,000 track-type tractors for the military. The company continued to grow during the postwar period, and in 1979, the Hi-Way Yellow paint used on all Caterpillar machines was replaced by Caterpillar Yellow, the color that Caterpillar machines are still known for today. Since the early 1900s, Caterpillar machines have been used to complete building projects all over the world, including the Panama Canal, the Hoover Dam, the Golden Gate Bridge, and China’s Three Gorges Dam; they have also been used in disaster recovery efforts all over the globe.