1935,1981 Bourne and Sagamore Bridges over Cape Cod Canal

Bourne: (Bridge Hunter; Historic Bridges; Satellite)

Sagamore: (Bridge Hunter; Historic Bridges; Satellite)

MDOT
Bourne is in the foreground, and Sagamore is in the background.

Both bridges have the same design, and they were "recognized as 1934 "Most Beautiful Steel Bridge" in Class A by the American Institute of Steel Construction (AISC)." [both BridgeHunters] Both bridges have a main span of 616' and were rehabilitated in 1981.

2010 photo by Jann Mayer via BridgeHunter-Bourne, License: Creative Commons Attribution (CC BY)

I learned of the Bourne Bridge because it was in the background of this photo of the Cape Cod Canal RR Bridge.

Steve Belcher posted, cropped
Winter has arrived - Good morning from the Cape Cod Canal vertical lift RR bridge

The Sagamore doesn't need approach trusses like the Bourne because it is built between two hills.

2021 Photo by Josh Schmid via BridgeHunter-sagamore

You can tell that Cape Code was a tourist area because both BridgeHunter pages have several postcard images.

Boston Public Library Flickr via BridgeHunter-sagamore, License: Creative Commons Attribution (CC BY)

This is one of several historical photos on the HistoricBridges-bourne page. The HistoricBridges-sagamore page also has some historical photos.
Obviously the canal was widened in 1935 because that is when all three of these canal bridges were built.  Both vehicle bridges replaced trunnion bridges. And this photo shows that the railroad bridge replaced a Strauss jack-knife bridge.

USACE, Cape Cod Canal posted
Passing the Sagamore Bridge, crowds lined the bridge and Canal banks to cheer on the parade of ships.
Douglas Butler shared
Sagamore Scherzer Double Leaf Bascule Bridge Bourne, MA. U.S Army Corps of Engineers, Cape Cod Canal.

A five-year Massachusetts study concludes that both bridges should be replaced for about $1b. It would replace today's 48' wide 4-lane bridges with 138' wide 6-lane bridges and restructure the roads at the ends of the bridges. The USACE, which would fund the replacement of the bridges themselves, is still studying replacement vs. major refurbishment. [May 2019: CapeNews] On Apr 3, 2020 the USACE decided to replace the bridges. [MDOT-background]

The replacement estimate was up to $2.2b in July 2021. [CapeNews, but I hit a paywall]

USACE via CapeCod
The 1916 canal was 100' and it was expanded to 480' in 1935. The new bridges improved the clearance from 41' to 135'.