See Britain First, 1925

The oil boom of the early 1920s, particularly at Shell's Signal Hill, California site, provided the company with an opportunity to penetrate the Los Angeles area with sales of Shell gasoline and petroleum products manufactured in its new refineries nearby. In 1922, Shell Company of California and Roxana Petroleum merged with Union Oil Company of Delaware to form a holding company called Shell Union Oil Corporation. Approximately 65 percent of the holding company's shares was held by Royal Dutch/Shell Group.

By the late 1920s, the company was actively laying pipeline across the country to transport oil from its Texas fields to the Wood River refinery. Shell Pipe Line Corporation, established in 1927 upon the acquisition of Ozark Pipe Line Corporation, also connected these fields to a new refinery built in Houston in 1929. This refinery was dedicated to manufacturing products destined for sale on the east coast of the United States and overseas. In 1929, Shell Petroleum Corporation, a forerunner of Shell Oil Company, purchased the New Orleans Refining Company, which later became one of Shell's largest manufacturing facilities.