Casco Bay Lines was operated out of Custom House wharf begining in 1907.

Permanent year-round ferry service to the islands of Casco Bay in Portland was first offered by the Casco Bay Steamboat Company in 1878.

As the popularity of the islands grew, there was enough business to support two ferry boat companies and in 1881 the Harpswell Line began to run as well. Due to the recession of the 1890s both companies eventually merged as the Casco Bay and Harpswell Steamboat Company in 1907. At that time the companies also consolidated their best and most popular vessels and operated out of the Custom House Wharf facility.

In 1919, the economic effects of World War I and mounting repair costs Casco Bay and Harpswell Steamboat Company went bankrupt and re-emerged as Casco Bay Lines in 1919/20. The fleet was also reduced to four boats; the Aucocisco, Maquoit, Emita, and Pilgrim.

The caption on this postcard reads, "Casco Bay Fleet at wharf, Portland, Maine." It was printed as part of the Maine Vacation series by the Tichnor Brothers printing company from about 1930-1945, which endeavored to bolster Maine tourism.