Standing as a sentinel of maritime history, Portsmouth Harbor Lighthouse is a beacon of light and a testament to the enduring legacy of navigational aids. Located in New Castle, New Hampshire, this historic lighthouse holds the distinction of being the tenth of eleven light stations constructed before the American Revolution.

In the annals of lighthouse history, the year 1771 marked a significant milestone. It was during this year that Royal Governor John Wentworth oversaw the construction of the original hexagonal wooden lighthouse at Fort Point. This shingled wooden structure, crowned with a copper roof and an iron lantern, stood as a guardian of the night, casting its radiance over the waters. Three copper oil lamps illuminated the way, guiding mariners safely through the darkness.

However, as the years passed, it became evident that the original tower required replacement. In 1804, an 80-foot octagonal wooden tower was erected approximately 100 yards east of the 1771 structure. This new tower, built under the watchful eye of civil engineer I.W.P. Lewis, was deemed to be in excellent condition when inspected in 1842. Lewis's report also noted that the construction of the Whaleback Lighthouse off the coast of Portsmouth presented an opportunity to reduce the height of the Portsmouth Harbor Lighthouse to 55 feet, a modification that was carried out in 1851. A Fourth Order Fresnel lens was installed in the tower in 1854, further enhancing its navigational prowess.

As time marched on, the second tower succumbed to the ravages of time and required yet another replacement. In 1878, on the original foundation of the 1804 tower, a new 48-foot cast-iron lighthouse tower was erected. This tower, lined with brick, represented a modernization of the navigational aid. Upon the completion of this new tower, the remnants of the 1804 structure were respectfully dismantled, but the legacy of the Portsmouth Harbor Lighthouse endured.

Today, this historic lighthouse casts a constant green signal that can be seen by mariners for up to 12 nautical miles. An acrylic cylinder surrounding the lens imparts its distinctive green hue. The lighthouse complex also includes the 1903 oil house, which was meticulously restored in 2004, and the 1872 keeper's house. The latter now houses the United States Coast Guard offices.

In recognition of its historical and architectural significance, the Portsmouth Harbor Lighthouse was added to the National Register of Historic Places on October 8, 2009. This esteemed designation, bestowed by the National Park Service, underscores the lighthouse's vital role in preserving maritime heritage (reference number: 09000816).

Presently owned by the United States Coast Guard, the Portsmouth Harbor Lighthouse is lovingly maintained by the Friends of Portsmouth Harbor Lighthouses organization, a chapter of the American Lighthouse Foundation (ALF). ALF has entrusted this dedicated group with the care of the tower, oil house, and wooden walkway. Since November 2008, the Friends have also been entrusted with the stewardship of Whaleback Lighthouse.

Visitors are welcomed to the Portsmouth Harbor Lighthouse through open houses held every Sunday from late May to mid-October. Ascend the 44 stairs and 7-rung ladder to the lantern room, where breathtaking ocean views await, including glimpses of Whaleback Lighthouse and Wood Island Life-Saving Station at the entrance to the Piscataqua River. Revel in elevated vistas of Fort Constitution, adjacent to the lighthouse, and marvel at the working fourth-order Fresnel lens, a maritime marvel in itself. Volunteers are on hand to share the rich history of this unique maritime complex, nestled between the shores of New Castle, NH, and Kittery, ME.

Access to the lighthouse is typically through the Coast Guard property. When the gate is open, visitors can park for free near the lighthouse. When the gate is closed, alternative viewpoints are available. Stroll to the end of Ocean Street, near the parking area, to catch a glimpse of the lighthouse. Additionally, Great Island Common and New Castle Beach in New Castle offer splendid vantage points to admire this iconic maritime treasure.