The USCGC Acacia (WAGL-406/WLB-406) is an Iris-class 180-foot seagoing buoy tender operated by the United States Coast Guard.

Acacia was a multi-purpose vessel, nominally a buoy tender, but with equipment and capabilities for ice breaking, search and rescue, fire fighting, logistics, oil spill response, and other tasks as well.

While her overall dimensions remained the same over her career, the addition of new equipment raised her displacement to 1,025 tons by the end of her Coast Guard service.

The Rush-Bagot Treaty had largely demilitarized the lakes, but the United States and Canada agreed to suspend some of its provisions during World War II.

[6] After the war ended, the treaty came back into full effect and all of Acacia's on-deck armament was removed, leaving only small arms for law enforcement actions.

Buoys were brought to port in the fall to prevent them from being damaged, sunk, or set adrift by ice.

Acacia was reported to have picked up about 150 buoys from the Detroit River and nearby waters in ten days in December 1948.

In January 1945, for example, the freighter James Watt with a cargo of coal for the Ford River Rogue factory became ice-bound in Lake Erie.

[16] On 1 June 1956 Acacia towed the disabled freighter George Hindman from the Saint Claire River where she was blocking ship traffic.

[18] A happier outcome was obtained after two freighters collided at the mouth of the Saint Claire River during the night of 26 August 1971.

In May 1975 Acacia sailed from Port Huron to the Coast Guard Yard in Curtis Bay, Maryland for major renovations.

The majority of Acacia's crew transferred to the freshly renovated USCGC Bramble and sailed their new ship back to Port Huron.

[26]After her refit, Acacia was assigned to Sturgeon Bay, Wisconsin, where she replaced USCGC Mesquite, which was beginning her own renovation.

[30] Though moved across Lake Michigan, Acacia remained responsible for maintaining the same fleet of 220 buoys from Calumet Harbor to Little Bay De Noc.

She arrived back in Grand Haven in April 1988, in time to replace buoys after the spring ice break-up.

[35][2] In December 1989, Acacia responded to the grounding of USCGC Mesquite off of the Keweenaw Peninsula in Lake Superior.

She was awarded the Coast Guard Meritorious Unit Commendation for her work, but winter storms destroyed the abandoned Mesquite.

There was no replacement cutter assigned to Grand Haven, reducing the number of buoy tenders in the Great Lakes from five to four.

Thousands did so, creating a crisis of unsafe small boats and rafts intent on reaching the United States.

By the time she reached the area, Operation Uphold Democracy, the United States intervention to restore Jean-Bertrand Aristide to the presidency of Haiti, was underway.

Acacia was retasked to survey and buoy the major ports that were used to support the operation including Port-au-Prince, Cap-Hatien, and Miragoane.

Immediately after decommissioning, Acacia was donated to the State of Illinois for the benefit of the American Academy of Industry.

The vessel, which was delivered in full working order with only her machine guns removed, was temporarily moored at Burns Harbor in Indiana.

Through the efforts of a common board member, the ship was transferred from the American Academy of Industry to The Society for the Preservation of the S.S. City of Milwaukee.

[45] On 16 October 2009, Acacia steamed under her own power to Manistee, Michigan, where she became part of the SS City of Milwaukee National Historic Landmark museum.