Part of the Atlantic Intracoastal Waterway, the canal is roughly 17.4 miles long (approximately 7 of which are cut through land) and connects Cape Cod Bay in the north to Buzzards Bay in the south. The 540-foot width of the canal is spanned by the Cape Cod Canal Railroad Bridge and two highway bridges -- the Bourne and the Sagamore. Traffic lights govern the approach of vessels over 65 feet, and are located at either end of the canal.
Canal engineers first needed to understand the theory of plate tectonics, because when the continents came together the bedrock was changed as a result. They needed to know what kind of bedrock they were dealing with. The engineers finally decided which route through the hillsides to take by connecting and widening the Manomet and Scusset Rivers.
On June 22, 1909, construction finally began for a working canal under the direction of August Belmont, Jr's Boston, Cape Cod & New York Canal Company, using designs by engineer William Barclay Parsons. There were many problems that the engineers of the canal encountered; one was mammoth sized boulders. Divers were hired to blow them up, but the effort slowed dredging. Another problem was cold winter storms, which forced the engineers to stop dredging altogether and wait for spring. Nevertheless, the canal opened on a limited basis in 1914, and was completed in 1916. The privately owned toll canal had a maximum width of 100 feet (30 m), a minimum depth of 25 feet, and took a somewhat difficult route from Phinney Harbor at the top of Buzzards Bay. Due to the narrow channel and navigation difficulty, several accidents occurred which limited traffic and blackened the canal's reputation. As a result, toll revenues failed to meet investors' expectations.
A German U-boat, the U-156, surfaced three miles off Orleans, on July 21, 1918 and shelled the tug Perth Amboy and her string of four barges. The Director General of the United States Railroad Administration took over jurisdiction and operation of the canal four days later under a presidential proclamation. The United States Army Corps of Engineers re-dredged the channel to 25 feet deep while it remained under government control until 1920. In 1928, the government purchased the canal for use as a free public waterway. The purchase price was $11,400,000, and $21,000,000 was spent between 1935 to 1940 increasing the canal's width to 480 feet, and its depth to 32 feet. As a result, the canal became the widest in the world. The southern entrance to the canal was rebuilt for direct access from Buzzards Bay rather than through Phinney Harbor.
During World War II, shipping again used the canal to avoid U-boats patrolling offshore. The canal was protected from coastal batteries at Sagamore Hill Military Reservation. The Mystic Steamship Company's collier Stephen R. Jones was grounded and sank in the canal on June 28, 1942. Shipping was routed around Cape Cod, and the SS Alexander Macomb was torpedoed on July 3 with the loss of 10 lives. The canal reopened on July 31, after the wrecked Stephen R. Jones was removed with the help of 17 tons of dynamite.