Maine's 9th annual Open Lighthouse Day is happening Saturday, September 9th.The 25 that will be free to tour on are only about 40 percent of the 66 lighthouses still standing in the state. There were at least 70 about a century ago.

mainetoday.com

The event draws more and more people every year. Last year there were anywhere from 15,000 to 18,000 people curious to see what's inside a Maine lighthouse. People come from all over the country to tour as many lighthouses as they can.

visitmaine.com

You may have to pay for parking, but entry and the tours of the lighthouses are absolutely free that day.