Navigation Structures at Pentwater Harbor

In 1855, Charles Mears constructed a 70-foot-wide (21 m) channel from Pentwater Lake to Lake Michigan, lined with timber cribbing,[1] to accommodate his lumbering interests.[5] In 1858, he built a pier extending over 600 feet (180 m) into Lake Michigan where ships could dock.[6] Additional pier structures were built to line the channel.[6] The first incarnation of the channel was relatively shallow, but Mears continued to improve it, and by 1865 it was deep enough that a lake-going steamer, the Daylite, was able to sail into Pentwater Lake.[1]

In 1868 the US government began widening and improving Mears's channel.[5] The channel was widened to 150 feet (46 m) and dredged to a depth of 16 feet (4.9 m).[1] Two piers were constructed, and in 1873 a timber-framed lighthouse, 33 feet (10 m) high,[1] was built on the south pier.[6] A red 6th-order Fresnel lens was installed.[1] A life-saving station was constructed on the north pier in 1887,[5] and in 1917 the pierhead light was automated.[1]

In 1937, the entire pier structure was replaced by the Army Corps of Engineers with a concrete pier.[1] At the same time, the timber-framed lighthouse was replaced with a steel skeleton structure,[6] and the optic replaced with a 12-inch (300 mm) lens.[1] Most of the life-saving station site, with the exception of the flag tower, was demolished in 1958.[5] A second light was erected on the north pier in 1997.[6]

The Pentwater navigational structures consist of two concrete piers extending into Lake Michigan. At the end of the north pier sits a cylindrical modified "D9-type" tower topped with a 300-millimeter flashing green acrylic optic at a focal plane of 43 feet (13 m).[1] At the end of the south pier sits a steel skeleton tower topped with a 300-millimeter flashing acrylic optic at a focal plane of 48 feet (15 m).[1]

• Harbor Infrastructure Inventories: Pentwater Harbor, Michigan (PDF), US Army Corps of Engineerins