Part of the Fitzgerald's operations were reorganized into a holding company in 1936, and later expanded about 1938 with equity funding from General Motors, Firestone Tire, Standard Oil of California and Phillips Petroleum for the express purpose of acquiring local transit systems throughout the United States in what became known as the General Motors streetcar conspiracy.

[2] The company formed a subsidiary, Pacific City Lines in 1937 to purchase streetcar systems in the western United States.

The company has roots back to 1920, when E. Roy Fitzgerald and his brother began operating two buses in Minnesota,[n 1][3] transporting miners and schoolchildren.

[n 3] In 1936, they bought 13 transit companies in Illinois, Oklahoma and Michigan, then in 1937, they replaced streetcars in Butte, Montana and made purchases in Mississippi and Texas.

[n 1] American City Lines, which had been organized to acquire local transportation systems in the larger metropolitan areas in various parts of the country in 1943 merged with NCL in 1946.

The larger local transportation systems include those of Baltimore, St. Louis, Salt Lake City, Los Angeles and Oakland.

The largest concentrations of smaller systems are in Illinois, with eleven cities; California with nine (excluding Los Angeles); and Michigan with four.

A star (*) indicates that NCL is understood to have had significant control but not ownership: Additional information: In Los Angeles the Los Angeles Railway (Yellow Cars) was controlled by NCL but not Pacific Electric Railway (Red Cars) Montgomery City Lines was the National City Lines subsidiary that operated the municipal transit system for Montgomery, Alabama.

[15] On 1 December 1955, Rosa Parks was arrested for refusing to move to the back of a Montgomery City Lines bus.

[15] The boycott ended only after the United States Supreme Court affirmed Browder v. Gayle, a ruling that black bus passengers had a right to sit in any publicly available seat.