In 1881, the Harpswell Line began providing regular service to the outer bay islands.

CBITD acquired CBL assets through bankruptcy proceedings to ensure the continuation of transportation service between their primary terminal hub in Portland, Maine, and the islands of Casco Bay.

CBITD is governed by a board of twelve directors, ten of whom are elected from the island communities.

The signature color patterns of the Casco Bay Lines fleet is (from bottom up): black, yellow, white and red.

The Portland Ferry terminal received a substantial renovation and addition in 2014 designed by Scott Simons Architects.

[3] Each of the seven islands on the roster of Casco Bay Lines is served seven days a week, with frequency dependent upon the season.

[7] The Wabanaki and Maquoit II share the running of the route, beginning at 5.00 AM each day in the high season.

In the summer of 2014, a major renovation and addition designed by Scott Simons Architects opened to the public, effectively doubling the size of the original building.