The heavy radars searched for attacking Soviet bombers but were unable to detect aircraft flying low to the west of the dunes along Lake Michigan.

The Saugatuck Gap Filler Annex was listed on the National Register of Historic Places in 2022,[1][2] and efforts are underway by a group of volunteers to stabilize the site and secure funding for further preservation and restoration.

In 1949, the only vestige of a North American continental air defense system was a motley collection of surplus WWII-era radars scattered sparsely across Canada and the northern United States.

With the sudden advent of the Soviet atom bomb and the TU-4, however, priorities were rapidly reassessed and the US Air Force launched an aggressive program to augment radar coverage of the most likely routes of attack from the north over Canada.

The Ground Observer Corps (GOC), disbanded at the end of World War II, had been brought back into service and greatly expanded to assist in visually identifying aircraft and estimating altitude.

The solution identified to address the issues with manual control was to use massive computers to analyze radar data, assess which defenses were most appropriate for a response, and automatically direct interception of suspected Soviet bombers, all with minimal human involvement.

The system that emerged to satisfy this requirement was SAGE, the Semi-Automatic Ground Environment, a continent-wide network of enormous AN/FSQ-7 computers linked to hundreds of radars.

Not all of the proposed sites were actually developed and, even if the buildings were constructed, not all received the radar equipment and towers as funds were slowly diverted to address the emerging threat of missile attack, highlighted by the launch of the Soviet Union's Sputnik satellite in 1957.

[8] Like the other three gap-fillers under the control of Custer AFS, the Saugatuck Gap Filler Annex was designed to be unmanned and was operated remotely by the prime site.

The squadron was directed to drain and flush the transmitter coolant systems, tape the doors of the equipment cabinets, and prepare the diesel generators for storage.

Occasional stop-gap work was performed to seal roof leaks and secure the site against souvenir collectors but, high atop the dune, it was basically out of sight, out of mind, and the condition of the annex steadily worsened.

SHPO, which acts as the gateway to the NRHP, concluded the annex was significant for its role in the nationwide Cold War SAGE system and appeared to merit listing on the Register.

Thus began an initiative to nominate the Saugatuck radar annex to the National Register, spanning five years, including three major drafts, and navigating the upheaval and government shut-downs of the COVID-19 epidemic.

The database of gap-filler sites gathered and maintained by The Air Defense Radar Veteran's Association at www.radomes.org was used to inspect each location via Google Maps satellite view to determine if any structures remained.

Stabilizing the structure and improving security against vandalism and trespassers emerged as the most effective immediate path, basically freezing the site in its present state to buy more time for consideration of long-term prospects.

With the aid of volunteers from other area organizations the work group removed the daunting mass of vegetation that had sprung up on the annex grounds, fences, and structures over the years, conveying a sense the site had been abandoned and providing a screen for vandals and trespassers.

Serious leakage issues threatening the roof structure and building interior were temporarily addressed and volunteers removed graffiti from the exterior walls, sealed gaps and voids in the cement block, and applied a new coat of paint all around.

An organization specializing in the preservation and rehabilitation of historic structures was consulted to suggest methods by which deterioration of the foundation and block walls could most effectively be addressed.

The lengthy process of listing the Saugatuck Gap Filler Annex on the National Register of Historic Places was successfully concluded in late 2022.

[2][1] In response to its listing, the annex was also subject of a special press release by the State Historic Preservation Office, an honor reserved for "particularly interesting National Register nominations."

Over the years there has been growing interest in improving Saugatuck area cell phone coverage, particularly at popular Oval Beach on the Lake Michigan shore 0.4 miles west of the radar annex.

In June 2023 the group commissioned a complete internal and external three dimensional laser scan of the tower, radome, and antenna structures as well as the equipment building and perimeter fences.

The Friends also provided the Saugatuck City Council with a position paper stating the importance of protecting the historical integrity of the AN/FPS-18 radar antenna which is a rare artifact, one of four known to have survived intact, one on display at a museum.