Established as a beacon at the  \'Harbor\'s Mouth\', as early as the late 1730s, the land where the Thames River meets Long Island Sound was purchased in 1759 for the construction of New London Harbor Light, also called the Pequot Light, in the reign of King George II. In 1761, with money raised by selling lottery tickets, a 64-foot stone tower with a lantern was erected at the west side of the harbor entrance.

New London\'s Shaw  family made a vast fortune in shipping during the colonial times leading to the American Revolution. At the start of hostilities in 1775 and under the permission of the Governor of Connecticut Johnathan Trumbull, Shaw began to outfit ships of line to wreak havoc on British supply ships. This type of legal piracy, also  known as privateering, was an extremely effective tool for the colonies, as there was not any serious American navy at this point. The ship owner and his investors would share in the profis of the goods that were taken and resold usually at the docks at escalated prices. A share would then go to the coffers of the state and everyone was happy.

New London Harbor lighthouse helped to guide Shaw\'s American privateers into New London Harbor. As a result of this activity, Benedict Arnold targeted and burned down New London in 1781, having landed his troops near the lighthouse.

New London Harbor Light was the fourth lighthouse recognized by George Washington when he enacted the 1789 Act for the Establishment and support of Lighthouse, Beacons, Buoys, and Public Piers.

By 1799, the lighthouse developed a large crack and there also were complaints that the light was difficult to distinguish from neighboring homes.

The current octagonal tower, designed by Abisha Woodward, was constructed of brownstone in 1801. New London Harbor Light was one of the earliest American lighthouses with a flashing light. The revolving eclipser gave it a distinct characteristic so it couldn\'t be confused with the lights of nearby houses. (This eclipser was not noted in Robt. Mills\'s American Phares,1832, so may have been installed later than noted.)

New London Harbor Light was extinguished during the War of 1812 at the request of Commodore Decatur. With the militia nearby the British decided not to raid the lighthouse, but they did raid Little Gull Island Light farther out in Fishers Island Sound.

The keeper\'s quarters were constructed in 1863 (enlarged in 1900). The station was automated in 1912 (possible date range based on construction of fog signal house, whose date is given as 1903 (discontinued 1911) and automation of light).

The lighthouse is mentioned in Eugene O\'Neill\'s play Ah Wilderness. and its former foghorn in the New London playwright\'s  Long Day\'s Journey Into Night.