CB&I, originally known as Chicago Bridge & Iron Co, is a global EPC firm that specializes in storage solutions for infrastructure and industrial projects. CB&I was founded in 1889 and is headquartered in The Woodlands, Texas. Initially known for its expertise in bridge construction, CB&I evolved over the years to focus on large-scale steel tank fabrication. According to one of the founder's heirs about present-day CB&I, "The old joke is that Chicago Bridge & Iron isn't in Chicago, doesn't build bridges and doesn't use iron."

The company designs, fabricates and installs storage tanks and terminals, pressure vessels, special plate structures, and complete storage process facilities. CB&I also integrates process equipment, piping systems, instrumentation, and control systems for storage operations. The company operates globally with facilities across North America, the Middle East, and Asia.

CB&I was founded by Horace E. Horton of Rochester, Minnesota when he moved to Chicago, Illinois in 1889. Horton, an experienced engineer, capitalized on the booming infrastructure needs of the era, initially focusing on bridge construction, which was essential for expanding rail networks across the Midwest. By the late 1890s, CB&I diversified beyond bridge construction, taking on projects such as railroad roundhouses, locomotive turntables, roof trusses and bulk liquid storage, coinciding with the western expansion of railroads across the United States and the discovery of oil in the Southwest. CB&I played a role in water infrastructure improvements, constructing elevated water tanks and standpipes to meet growing municipal needs. CB&I quickly became known for design engineering and field construction of elevated water storage tanks, above-ground tanks for storage of petroleum and refined products, refinery process vessels and other steel plate structures. CB&I was at the forefront of several technological advancements, including the construction of the world’s first field-erected spherical pressure vessels (Hortonsphere vessels) and the development and commercialization of the floating roof by John H. Wiggins, which revolutionized petroleum storage by improving safety, reducing evaporation losses, and minimizing tank corrosion. As such, CB&I supported the expansion of oil exploration outside the US, starting operations in South America in 1924, in Asia two years later and in the Middle East in 1939. Also in the 1920s, CB&I entered into licensing agreements with European counterparts like Motherwell Bridge & Engineering Ltd. and Whessoe Ltd.

During the 1930s and 1940s, under the leadership of George Horton, CB&I transitioned from riveted to welded plate metal construction, improving structural integrity, reducing construction time, and enhancing project efficiency. Another significant development at this time was the company’s entry into nuclear-related projects such as the construction of nuclear storage tanks for DuPont at Hanford, Washington.

During World War II, CB&I was selected to build Landing Ship Tanks (LSTs), which carried troops and supplies to American and Allied troops fighting in Europe and the Pacific theater. CB&I was chosen because of their reputation and skills, particularly welding. Since the coastal shipyards were busy building large vessels for the war effort, such as aircraft carriers, battleships, cruisers and destroyers, there was no alternative but to use the inland waterways and shipyards for the production of smaller ships. CB&I’s Seneca, Illinois shipyard played a crucial role during the war, constructing 157 LST vessels for the US Navy. As a result of these and other wartime production activities, CB&I ranked 92nd among US corporations in the value of World War II military production contracts.^{[verification needed]}

Following World War II, CB&I transitioned from wartime shipbuilding to peacetime industrial projects, adapting to post-war market demands. The company underwent a transformative period marked by significant achievements in nuclear engineering and technological innovation. One notable project of this era was a 225-foot-diameter containment vessel CB&I constructed at the Knolls Atomic Power Laboratory in West Milton, New York, which was used to test the atomic reactor for a prototype nuclear submarine. In 1955, CB&I connected a nuclear engine to the commercial electrical grid, marking the first instance of nuclear energy being generated and sold commercially. That same year CB&I erected liquid oxygen spheres at Cape Canaveral to support the US space program that eventually put a man on the moon. In 1960, CB&I built the world’s first large, liquefied natural gas (LNG) tank in Lake Charles, Louisiana.

By 1967, one third of CB&I’s business was outside the US, with subsidiaries operating across Europe, the Middle East, Africa, and Asia. Some notable projects from this time include refineries in Nigeria, wind tunnels in Canada, and oil terminals in Hong Kong. In 1969, CB&I introduced innovative offshore oil storage with "Khazzan Dubai No. 1," which was constructed onshore and towed to the site using a cushion of air, demonstrating novel deployment techniques for underwater oil storage. The National Society of Professional Engineers recognized the project alongside the Apollo Moon Project as one of the outstanding engineering achievements of the year.

Jim Maher was named Director of Research in 1977. Under his leadership, the company’s research efforts focused on enhancing materials, methods, and designs. One notable study was conducted jointly by CBI and Standard Oil with the goal to more accurately predict hydrocarbon emissions from floating roof tanks. Also in 1977, the company went public listing their shares on the New York Stock exchange under the ticker CBI. In 1979, shareholders approved a reorganization to create CBI Industries, Inc. CBI Industries became the parent company, with Chicago Bridge & Iron Company as its wholly owned subsidiary.