Why is it a historical location? I've never heard of it other than it's image is used for The Lighthouse in the MCU show Agents of SHIELD.

It was the first lighthouse in maine. Built when maine was still part of Massachusetts. The US government, and president George Washington financed a large portion of the cost, MA paid for the remainder. (Less that 3000 total!) Also the entire park is known as Fort Williams. It was a military base/fort that was active during WW 1.

Longfellow, who lived in Portland, would walk there for inspiration. It has been there forever. There are myriad other reasons that I just don't know.

https://en.m.wikipedia.org/wiki/Annie_C._Maguire

For many reasons - some of which include the directive from George Washington to build the lighthouse and to protect Portland Harbor during the Civil War.