Operating in over 54 countries, McDermott has more than 30,000 employees, as well as a diversified fleet of specialty marine construction vessels and fabrication facilities around the world.

Knowing he could benefit from his father's long-time experience in the lumber and oilfield construction businesses, Ralph made John Raymond McDermott a partner and the company's namesake.

In 1930, it expanded the business from its original headquarters in Eastland, Texas, to Luling after a boom in oil exploration in the area.

The following year, the company designed and installed the first fixed platform made of steel out-of-sight-of-land, in 20 feet of water in the Gulf of Mexico for Superior Oil.

In 1948, it acquired assets of Harry F. Allsman Company, McDermott's joint venture partner for several contracting jobs in the Gulf of Mexico, which provided equipment to meet the new demand for offshore construction.

[5] On December 18, 2017, CB&I and McDermott agreed to combine and form a fully vertically integrated onshore-offshore company.

[10] In August 2018, McDermott signed a contract with Shell to work on the Perdido development in the Gulf of Mexico.

[15] On January 21, 2020, McDermott announced that it had filed for Chapter 11 bankruptcy, cancelling all shares of common stock.