Plum Island
Geography

Plum Island Show map of Wisconsin Plum Island Show map of the United States
Location	Door County, Wisconsin
Coordinates	45°18′29″N 86°57′11″W / 45.308132°N 86.953142°W / 45.308132; -86.953142
Area	0.455 sq mi (1.18 km²)
Highest elevation	610 ft (186 m)
Administration
United States
State	Wisconsin
County	Door County
Town	Washington Island

Plum Island is an island in Lake Michigan in the southern part of the town of Washington in Door County, off the tip of the Door Peninsula in the U.S. state of Wisconsin.^[1] The uninhabited island has a land area of 1.179 square kilometres (0.455 sq mi) or 117.87 hectares (291.3 acres). Carp Lake is located on the northwestern side. During years when Lake Michigan's water levels are high, it is a lagoon of Lake Michigan, but it gets cut off as a separate lake during low water years.^[2]

The island is a bird sanctuary under control of the United States Fish and Wildlife Service and part of the Green Bay National Wildlife Refuge since 2007,^[3] and is open to the public for recreational purposes.^[4] The island also holds the unmanned Plum Island Range Lights and now-closed Plum Island Lifesaving Station.

Border Dispute

The border between Wisconsin and Michigan was originally defined as "the most usual ship channel" into Green Bay from Lake Michigan but commercial routes existed both to the north and south of the island which led to a border dispute. In 1936, the U.S. Supreme Court decision Wisconsin v. Michigan found that Plum and other nearby islands were part of Wisconsin.

Climate

Plum Island

Climate chart (explanation)

J	F	M	A	M	J	J	A	S	O	N	D
66 −4 −9	60 −8 −10	62 0 −4	112 3 0	86 9 3	77 13 10	96 18 16	73 19 16	109 17 14	119 10 7	110 6 5	66 4 1
█ Average max. and min. temperatures in °C
█ Precipitation totals in mm
Source: ^[5]

Imperial conversion
J	F	M	A	M	J	J	A	S	O	N	D
2.6 25 16	2.4 18 14	2.4 32 25	4.4 37 32	3.4 48 37	3 55 50	3.8 64 61	2.9 66 61	4.3 63 57	4.7 50 45	4.3 43 41	2.6 39 34
█ Average max. and min. temperatures in °F
█ Precipitation totals in inches

Lifesaving Station and Range Lights

A lighthouse was built on the island in 1848, but abandoned when it was decided to move it to nearby Pilot Island in 1858. The island was re-colonized in 1895–6, when both a lifesaving station on the Northeast corner and a set of range lights on the Western side were built. The lifesaving station operated from 1895 to 1991, before being moved to nearby Washington Island, while the range lights were automated in 1969 and remain an active aid to navigation.^[6]

Shipwreck

The wreck of the Grape Shot is 0.18 miles NW of the lifesaving station in 8 feet of water. It sank in 1867 after being driven ashore in a gale while carrying a cargo of lumber.^[7]