Deer Isle Causeway

Connecting coastal communities to the mainland, as a vital ingredient of a vibrant fisheries and working waterfronts to underlie a thriving Maine economy.


Annually, thousands of vehicles, people, pounds of product, lumber, fuel, water and other vital needs move across a delicate thread of a transportation corridor that links one of Maine’s most remote island communities to the mainland. When initially created, the causeway was built on an existing sandbar that was topped by water during mid-high tides. 

This location was known as the K’chisitmokan’gan or “Great Fish Weir” by indigenous people for its service as a choke point for gathering fish during tidal changes. This “new” geologic feature supports some of Deer Isle-Stonington’s most productive clamming flats and where shellfish landings are consistently among the highest in the state of Maine.


Recent January 2024 back to back historic storms and tide surges rocked the Deer Isle-Sedgwick causeways and bridge like none before, and left many towns without power, isolated by washed out roads, landslides, and flooding for days. Photo credit: Maine DOT

Updates & Events

Maine DOT Public Meeting

  • Wednesday, June 5, 2024 from 6:00 p.m. – 7:30 p.m. Reach Performing Arts Center 249 N Deer Isle Road, Deer Isle
  • To discuss draft findings from a Feasibility Study related to causeway improvements, and address & respond to public comments submitted during the May comment period.

Maine DOT Story Map public viewing

  • "How-to-comment” instructions and discussion.
  • May 7, 2024 Deer Isle Town Offices 5 - 6:30 p.m.

The Challenge

The communities and municipal leaders of the Towns of Stonington and Deer Isle have identified a critical need to support long term community resilience and comprehensive planning of coastal connectivity through preservation of working waterfronts, wharf infrastructure and transportation corridors. The vital island-to-land connectivity provided by the Deer Isle Causeway has economic implications to the entire community and State of Maine tourism and fisheries industries. Through the course of recent scoping efforts to assess Causeway upgrades, questions of environmental impact on surrounding fisheries emerged as we evaluate options for adaptation that preserve the integrity of our community and ecosystems.

The Opportunity

Hydrological forces shape the immediate Eggemoggin Reach and surrounding area are truly unique, and knowing more about these circulation patterns provides community members with vital data to guide informed opinion. 

The Deer Isle Causeway and surrounding area tidal flow all stopped in 1938 when the causeway was completed, preventing any flow of water from one side of the bar to the other. Motivated by the question of how fisheries such as scallops, clams, and other sensitive fisheries species could be impacted by the alternatives considered for Causeway improvements, MCCF worked with partners to generate new data and model the flow patterns.

By exploring the potential environmental impacts of Causeway engineering options before initial public outreach we are able to provide critical scientific data to support proactive thoughtful adaptation to changes we face – just in time as the public discourse gets under way.

Herbie Carter, fisherman and clam digger native to Deer Isle, digs for clams on northeast side of the Deer Isle Causeway. Photo credit: Tate Yoder, MCCF

The Deer Isle Causeway connects one of Maine's most remote island communities to the mainland. Photo credit: Tate Yoder, MCCF

Our Aim & Approach

This work connects directly to the Coastal and Marine Working Group of the Governor’s Climate Council, where our Chief Scientist contributes to review and update the Maine Climate Action Plan entitled “Maine Won’t Wait.”

Recent January 2024 back to back historic storms and tide surges rocked the Deer Isle-Sedgwick causeways and bridge like none before, and left many towns  without power, isolated by washed out roads, landslides, and flooding for days. Extreme storms like this are a wake-up call: what we thought could happen in 20 years’ time, might actually happen in less than five.

MCCF’s experience, relationships, and expertise help to surface and capture the values and priorities of the community, ensuring that the local ecological knowledge of vital Maine fishing communities are injected into the solution set discussions. This strengthens and protects our infrastructure and natural resources, for the communities and industries that rely on them.


And most importantly the municipal leadership, residents, and fishermen of Deer Isle, Stonington and Sedgwick that rely on this causeway every day.

Cited Literature & Further Resources

Maine DOT Deer Isle Causeway Project StoryMap. 

The above link is the MDOT StoryMap for the entirety of the Deer Isle Causeway project. The latest presentation and feasibility study are linked here. Also see several photos and images that can be harvested for this page.