Editor’s note: this is the 14th in a series of articles covering the region’s dramatically changing coastline. Click here to see all of the articles.

The changing shape of the Cape & Islands Lewis Bay: From Hyannis Port to Kalmus Beach & Great Island, May 2017 Cape Cod LIFE | capecodlife.com

A recent northeast-facing view of Lewis Bay, a busy body of water that serves as the natural border between Barnstable and Yarmouth. Boats can be seen traveling in and out of the bay to Nantucket Sound through the federal navigation channel. Above, one can view Kalmus Beach, the Hyannis Yacht Club, and the entrance into Hyannis’ Inner Harbor, while at right, one can see Egg Island, which is part of Barnstable, and Great Island, a privately owned section of Yarmouth. In the 19th century map, Egg Island and other islands stand on their own in the bay. 1880 map courtesy of the Historical Society of Old Yarmouth. Photo by Paul Rifkin

Lewis Bay is part of the south coast of Cape Cod, basically the center of the triceps when thinking of the “arm” of Cape Cod. The bay measures some 1.6 square miles and serves as a natural border between Yarmouth to the east and Hyannis to the west. Those who travel on ferries out of Hyannis travel through Lewis Bay to get to Nantucket Sound, passing Hyannis’ Kalmus Beach and Yarmouth’s Great Island. The bay is named for Jonathan Lewis, an 18th-century Cape Codder who was the first Hyannis resident to construct a two story home.

As the Steamship Authority and Hy-Line both run ferries in and out of Hyannis’ Inner Harbor, the bay is a busy transportation channel. Brian Braginton-Smith, executive director of the Lewis Bay Research Center, describes Lewis Bay as a “lifeline” connecting Cape Cod and the islands. He also describes the bay’s geography as “like a shallow bowl. The waves wash up on shore, then reverberate back and forth.” It’s the regular use of this “lifeline” that has brought about substantive changes in the “shallow bowl” during the past 70 years.