Portland Head has long protected Portland and the adjacent area. Cape Elizabeth residents were deeply committed to American independence from British rule. In 1776, the new Town of Cape Elizabeth posted a guard of eight soldiers at Portland Head to warn citizens of coming British attacks.

In 1787, the General Court of Massachusetts (the Massachusetts legislature) provided $750 to begin construction of a lighthouse. In 1790, when the United States Government took over the responsibility of all lighthouses, Congress appropriated $1,500 for its completion. The original tower measured 72' from base to lantern deck and was lit with 16 whale oil lamps. It was first lit on January 10, 1791.

Construction of the first Keeper's Quarters began in 1790 as the result of a contract signed by Massachusetts Governor John Hancock. A one story dwelling built to replace the first keeper's house was erected in 1816. It measured 34' x 20' with two rooms, a cellar and a porch in the rear.

By 1864 a 4th order Fresnel lens and a cast iron staircase were installed.

By 1865, the tower was raised 20' and a 2nd order Fresnel lens was installed. A portion of this lens may now be seen at the Museum at Portland Head Light. Except for a period between1883 and1885, this lens was in the lighthouse until 1958.