In the early 1920's the California Transportation Company, the leading passenger carrier on the Sacramento and San Joaquin rivers, announced plans to build two modern passenger vessels for its Sacramento to San Francisco run. In 1927, the Delta King and Delta Queen, with a combined length of 500 feet, became the largest vessels ever to regularly operate on the Sacramento River. For the first time in Sacramento's history, the foot of M Street became the central point of passenger service with the introduction of these deluxe boats.
In 1932, the active Sacramento River transportation companies joined forces and began operating under a joint agreement. Technically, the companies were not merged but ran under the common name "The River Lines." Decline in passenger traffic in the late 1930s resulted in The River Lines ending passenger service on the river in 1940. The Delta King and Queen were put up for sale the following year. The Delta King was returned to Sacramento in 1984 and opened as a waterfront hotel and restaurant in 1989.