Caterpillar Inc. is an American construction conglomerate. It is widely accepted as the largest construction equipment manufacturer in the world. The company specializes in the manufacture of construction and mining equipment, diesel and natural gas engines, industrial gas turbines, as well as diesel-electric locomotives. It operates through the following segments: Construction Industries, Resource Industries, Energy and Transportation, Financial Products, and others. Caterpillar Inc. is consistently ranked in the top 100 on the Fortune 500 list of largest American companies by revenue. Caterpillar stock is tracked on the Dow Jones Industrial Average, confirming its status as one of the most important US companies engaged in industrial activities. Caterpillar Inc. came about from the 1925 merger of the Holt Manufacturing Company and the C. L. Best Tractor Company, creating a new entity, California-based Caterpillar Tractor Company. Although primarily a heavy machinery construction company, Caterpillar also manufactures and markets a line of clothing and workwear boots under its brand name. The company also produces the Cat phone brand of industrial-strength mobile phones.