Skidmore, Owings & Merrill (SOM) is an American architectural, urban planning, and engineering firm. It was formed in Chicago in 1936 by Louis Skidmore and Nathaniel Owings; in 1939 they were joined by John O. Merrill. The firm opened its second office, in New York City, in 1937 and has since expanded all over the world, with offices in San Francisco, Los Angeles, Washington, D.C., London, Hong Kong, Shanghai, Mumbai and Dubai. SOM is one of the largest architectural firms in the world.