Caterpillar Tractor Co. of Peoria, Illinois, made the crawler tractors the U.S. Army Engineers chose for their own troops. From 1942 to 1945 it built 56,306 crawlers in five models: the D2, D4, D6, D7 and D8.
This timeline follows the company from its formation in 1925 to its return to civilian work in 1946. Figures and quotations are given as the sources state them; where sources disagree, the note under each entry says so.
Before the war
01
Holt and Best merge to form Caterpillar Tractor Co.
Holt Manufacturing Company and C.L. Best Tractor Co. merge to form Caterpillar Tractor Co. In Caterpillar’s account, Best brings “the domestic market, an advanced dealer network and expanded product line,” and Holt brings “a worldwide reputation, the ‘Caterpillar’ name and modern manufacturing facilities.”
The former Holt plant in East Peoria, Illinois, becomes the company’s largest manufacturing centre.
Sources & notes 1
Caterpillar’s merger page gives the year only. The often-cited April 1925 date was not verified.
The Diesel Sixty, Caterpillar’s first diesel tractor
Caterpillar begins producing its first diesel tractor, the Diesel Sixty. A wartime Caterpillar brochure says the first one, serial 1C1, was sold and delivered in September 1931. The same year the company changes its standard paint from gray with red trim to “Hi-Way Yellow” with black trim.
Caterpillar states that “by 1936, Caterpillar produced nearly half of all diesel engines in the United States,” and that by the end of the 1930s it “was the largest diesel engine manufacturer in the world.”
Sources & notes 2
Jackson dates Caterpillar’s lead in diesel production to 1934. This page uses Caterpillar’s own wording.
Caterpillar dealers sell LeTourneau blades and scrapers
R.G. LeTourneau, Inc. begins a ten-year arrangement under which Caterpillar dealers sell LeTourneau blades and scrapers. LeTourneau builds a factory in Peoria, about three miles from the Caterpillar plant across the Illinois River.
In the war, completed Caterpillar tractors are trucked from East Peoria to the LeTourneau plant to have blades fitted.
The RD diesel crawlers are renamed D4, D6, D7 and D8
From 1935 the diesel crawlers carry “RD” names: RD4, RD6, RD7 and RD8. In 1938 Caterpillar drops the prefix, and the models become the D4, D6, D7 and D8. On the D7 the change falls at serial 9G6501.
Sources & notes 2
The renaming rests on Contractor Magazine, a trade publication. Caterpillar’s own article on the names could not be retrieved.
The Engineer Board tests a Cleveland Tractor Co. bulldozer with the 5th Engineers. Against a mule team with a slip scraper, the 4½-ton tractor with one operator “moved sixteen times as much dirt.”
Capt. Gilbert E. Linkswiler notes that Allis-Chalmers, International and Caterpillar “could offer similar models,” and recommends a 7½-ton medium dozer as standard equipment.
The Office of the Chief of Engineers approves a small number of tractors for engineer regiments and battalions as organizational equipment, with 15-ton bulldozers stocked in depots for rear-area work.
Four companies build construction-type tractors: Allis-Chalmers, Caterpillar, Cleveland Tractor and International Harvester. Together they make about 20,000 tractors in 1939, “but many of these were low-powered machines for which military demand was small.”
Army Ordnance asks Caterpillar to convert the Wright R-1820 Cyclone aircraft engine into a diesel tank engine. Caterpillar forms the Caterpillar Military Engine Company and builds a government-funded plant at Decatur, Illinois.
By January 1942 Caterpillar has a prototype of the diesel radial, later named the RD-1820.
The Army’s official history of the Corps of Engineers states: “The Engineers had a great deal at stake for they had settled upon the Caterpillar tractor for their own troops to the exclusion of other makes.”
In 1942 tractors and other construction machinery make up almost 40 percent of the $651,000,000 in Engineer deliveries.
Sources & notes 1
The Engineers’ tractor classes were named after Caterpillar models, but the D-8 class also included the Allis-Chalmers HD-14 and the Cleveland FD. Class totals are not Caterpillar-only counts.
The standard Navy construction battalion is allotted crawler tractors in four classes “ranging from 113-drawbar horsepower to 35-drawbar horsepower”: eight of class one, four each of classes two and three, and two of class four, all with dozers or angledozers. Jackson matches these to 8 D8, 4 D7, 4 D6 and 2 D4.
The Navy does not buy its own: “All lumber and crawler-tractor procurement had been placed in the hands of the Army early in the war, and the Army divided its supplies with other services.”
Sources & notes 2
The Navy’s allowance names drawbar-horsepower classes, not makes or models. The match to Caterpillar models is Jackson’s.
Tractor production is allocated to the armed forces
The War Production Board agrees “to assign 85 percent of tractor production to the armed forces.” The remaining 15 percent is kept for civilian use. Prime-mover tractors are bought by the Ordnance Department and construction tractors by the Corps of Engineers.
The 85 percent includes Lend-Lease, most of it for Britain. Between August 1941 and March 1942 Britain requisitions 2,300 tractors; in March 1942 it is told to expect no deliveries until December.
In June 1942 Caterpillar asks for 72,422 tons of steel and receives 47,653. On 29 June the chairman of its executive committee writes to the Army that the company is assembling tractors at about 50 percent of capacity and is holding 398 finished tractors for lack of shipping instructions: “I realize that thirteen million dollars sounds like two bits in Washington, but to us it is still a whale of a lot of money, and it is a lot of iron.”
In September the Army learns that engineer troops need $12,000,000 worth of Caterpillar spare parts. By early October, after working with Army production staff, Caterpillar has increased its expediters “from a handful of persons to seventy.”
Caterpillar forms the 497th Engineer Heavy Shop Company
The Corps of Engineers asks Caterpillar to form the 497th Engineer Heavy Shop Company, described as “the first unit in American history organized by a manufacturing company and manned primarily by its own employees.” Of the 191 men sworn in in September 1942, 158 are Caterpillar employees. The unit is activated on 1 October 1942.
The Engineers also use Caterpillar and LeTourneau, “their prime contractors for construction machinery,” to train operators and maintenance men for Army units.
The War Department issues TM 9-1773, Ordnance Maintenance: Heavy Tractor M1 (Caterpillar D7). Its supply catalog reference, SNL G-89, reads “Tractor, heavy, M1, caterpillar RD7 (Diesel).”
From 1943 the Engineers’ own manuals name the machine by class: “Tractor, Crawler, Diesel, 70 to 90-DBHP, Standard, Caterpillar, Model D7, 74-in. Gage.”
Sources & notes 2
Jackson gives Tractor, Medium, M1 for the D6 and Tractor, Light, M1 for the D4; neither was seen in a primary document. Sources disagree on whether the D8 had a military designation. No designation was found for the D2. TM 5-3068 was first authenticated on 1 June 1943 and reissued on 19 March 1945.
At the start of 1941 Caterpillar has about 11,000 employees in Illinois and California. In the year after the war begins, employment “rose from 11,000 to over 20,000 people.”
Caterpillar records that “in 1943 alone, 3,000 women worked in jobs on the factory floor,” and that women worked “in research, the foundry, and the assembly lines.”
Sources & notes 2
A figure of 30–40 percent women in the wartime workforce appears online but was not verified. The 3,000 is Caterpillar’s own.
The East Peoria plant receives the Army-Navy “E” Award for crawler tractor production. Stars follow on 24 May 1944, 25 November 1944 and 9 June 1945.
The San Leandro, California, plant, which makes 37 mm shell projectiles and diesel fuel-injection parts, receives the award on 16 February 1945, with a star in August 1945. The Caterpillar Military Engine Company plant at Decatur receives it on 26 June 1945 for D7 production.
Sources & notes 1
The award dates rest on one secondary source, Jackson.
The first M4A6 Sherman, powered by the Caterpillar RD-1820 diesel radial, is completed at the Detroit Tank Arsenal. Rickard rates the engine at 450 hp at 2,000 rpm.
Production ends in February 1944 after 75 tanks. Jackson says only 120 RD-1820 engines were built at Decatur, and that the plant was then converted to building D7 tractors.
Sources & notes 2
Jackson dates the first tank to October 1943. The sources differ on the original order: Jackson says 750 tanks were ordered; Rickard says 775 engines were allocated to the M4A6 from a January 1943 order for 1,000.
The 497th Engineer Heavy Shop Company is based at Shingbwiyang, Burma, at mile 103 of the Ledo Road, known as “Little Peoria.” It maintains Caterpillar D7 and D8 bulldozers, motor graders and other equipment.
In January 1945 the first convoy crosses the Ledo (Stilwell) Road, led by Brig. Gen. Lewis A. Pick.
In the obstacle-clearing landings on Omaha Beach, the Army’s account records: “Of 16 dozers only 6 got to the beach in working condition, and 3 of these were immediately disabled by artillery hits.”
Later on D-Day, “dozers under fire from snipers cut a road up the western slope” of the E-1 draw.
Sources & notes 1
The Army account does not give the makes of these dozers. Eight of those in the 116th RCT’s sector were tank dozers, Sherman tanks with blades.
From 1942 to 1945 Caterpillar builds 56,306 crawler tractors: 3,995 D2, 15,978 D4, 6,115 D6, 20,503 D7 and 9,715 D8. Yearly output rises from 9,606 in 1942 to 19,444 in 1945. These figures are from the Caterpillar Archives, as published by David D. Jackson.
The D7 increases most, from 2,255 in 1943 to 7,885 in 1944. Of the 20,503 D7s, 17,444 go to the U.S. Army. Caterpillar’s own history gives “approximately 51,000 track-type tractors for the military” over the same years.
Sources & notes 2
56,306 is total production; some 1945 output was civilian. The gap of about 5,000 between it and Caterpillar’s military figure is consistent with civilian and other non-military output.
Caterpillar introduces “the first company-designed-and-built bulldozer blade.” In the war, the blades on its tractors came from other makers, among them LeTourneau and LaPlant-Choate.
Sources & notes 3
Caterpillar dates the blade to 1945; Jackson says Caterpillar began making its own bulldozers in 1946.