COWI was founded by Christen Ostenfeld in Copenhagen. After completing his studies to become a qualified engineer Ostenfeld spent six years working abroad before returning to Denmark. He was 29 years when he founded his business in 1930. Initially worked from his small apartment in Vesterbro - a working class district in the city. His aim was to bring ‘academic knowledge into practical engineering’. The following year he won a prestigious contract to rebuild the Scala Theatre in Copenhagen which was by then in a very poor state. The company website describes how he used prefabricated steel elements that enabled the contract to be completed in less than a year. He continued using this style of construction including long-span roofs. By the early 1940s he had moved into designing small bridges around Denmark but as his reputation grew won contracts for bigger structures leading to the contract for the Aggersund Bridge. This consisted of two large bow-string girder spans connected by a double leaf bascule in the centre of the river to allow tall ships to pass through.

In the late 1940s the company became a leader in the use of pre-stressed concrete. Wriborg Jonson then became an equal partner in the form which was renamed Ostenfeld & Jønson - Rådgivende Ingeniører (Engineering Consultants) or O&J for short.

Through the 1950s and 60s the company expanded its international folio gaining contracts in Europe, Africa, the Middle East and America. In 1965 they won the contract for the design of the New Little Belt Bridge which has been described as the ‘most advanced suspension bridge’ at the time of construction. The design team introduced new technologies such as analysis of the risk of ship collisions; an aerodynamic bridge deck; and specially designed anchor blocks that suited the difficult soil conditions.

The company basis was changed to be foundation-owned after Christen Ostenfeld's retirement in 1973 and it was at this point that it was re-named COWI – which is an abbreviation of the two senior partners' names: Christen Ostenfeld and Wriborg Jønson.

The company has continued to expand in the 21st century winning contracts around the world. In addition to a variety of bridge contracts COWI has moved into the environmental and renewable energy market.

In 2020 COWI was among the design team for the new Water Street Bridge in Canary Wharf working in collaboration with Eadon Consulting and Knights Architects.

By 22024 the company has been involved in more than 50,000 projects in 175 countries and has approximately 7,300 employees, including engineers, biologists, geologists, economists, surveyors, anthropologists, sociologists and architects.

References: https://www.cowi.com/who-we-are/our-story/ https://en.wikipedia.org/wiki/COWI_A/S