AUGUSTA — Lighthouses along the coast of Maine will open their doors Saturday to the public as the state celebrates its fourth annual Open Lighthouse Day.

The United States Coast Guard has partnered with the Maine Office of Tourism and the American Lighthouse Foundation to sponsor the event, which will allow the public to visit 21 lighthouses.

Some of the lighthouses such as Seguin Island Lighthouse off Popham Beach and Monhegan Island Lighthouse can only be reached by boat while others such as Portland Head in Cape Elizabeth can be accessed on foot.

The event will take place Saturday. Hours could vary at each lighthouse and there are restrictions, such as the number of visitors that can tour the lighthouse, in effect at certain lighthouses.

“Tourism is one of our biggest industries, and I am proud to have the opportunity to show off our great state,” Governor Paul R. LePage said in a statement.