Door County Basics

I've been collecting these odds and ends about the peninsula for some time and it's about time I shared them with my readers. 

Conventional wisdom suggests that the permanent, year-round population of Door County is only about 26,000 individuals.  According to the last census (2020) the figure is 30,000.  Either way, the total for the entire county is significantly smaller than the population of 48,000 individuals that live in my former hometown of Wauwatosa.  We're small, basically rural with the major population center and industrial hub being Sturgeon Bay.

Door is a curious name for a county dontcha think?    The peninsula takes its name from the treacherous passage and dangerous shoals found between the tip of the peninsula and Washington Island.  The passage is littered with shipwrecks and thusly the early French explorers dubbed it:  Porte des Morts.  Which literally translates to death's door or door of the dead.  The completion of a ship canal in 1881 connecting Sturgeon Bay with Lake Michigan allowing shipping access to and from the bay of Green Bay and Lake Michigan eliminated the longer, time-consuming and dangerous passage around the tip of the peninsula.

Door County consists of 2,370 square miles of which 482 is Terra Firma and 1,888 (80%) being water.  There are 298 miles of coastline.  Only the islands that make up Hawaii have more coastline.  Door county's coastline is home to 11 lighthouses.  Only Long Island's Suffolk County has more lighthouses.  Speaking of shoreline, with the construction of the ship canal (see above) everything north of Sturgeon Bay is technically an island.  Albeit and artificial island but cut-off from the mainland nonetheless.  

The existence of the peninsula is a consequence of the Niagara Escarpment - a very tenacious formation of dolomite limestone that extends all the way from Buffalo, New York through the Fox Valley.  Multiple glaciations were unsuccessful in scouring it from the face of the earth. 

About 10,000 years ago when the last ice age visited Wisconsin my part of the world was buried beneath an ice sheet almost a mile thick. The earth's crust is still rebounding from the weight of all of that ice.  

Looking at this map you can see how the escarpment transects the peninsula. Visualize the Lake Michigan lobe of the glacier extending south just to the right of the line and the Green Bay lobe of the glacier extending south immediately to the left of the line.  This saucer-shaped geological feature formed from the basin of an ancient inland sea during the Ordovician and Silurian eras some 445 to 420 million years ago.  

Over a period of eons layers of limestone, sandstone and shale were laid down.  The western edge of the escarpment in Wisconsin curves in a semi-circular ridge northeast from Horicon Marsh, toward the eastern edge of Lake Winnebago and the western shore of Door County.  It arcs around Lake Huron, then south through Ontario and ends at Niagara Falls, spanning a total of 650 miles. Some of its edge is underwater or covered by glacial deposits, but much is exposed as cliff outcroppings as high as 200 feet in places.  Geologically-speaking these are old rocks. 

They also happen to be home to some exceedingly-old trees.  Because growing on these cliffs are some of the slowest-growing trees on the planet.  Door County is home to an ancient, old-growth forest.  

Photo - Wisconsin DNR




Three years ago some guys used an incremental borer to extract cores from four of the white cedar trees growing along the edge of the Niagara Escarpment at The Clearing in Ellison Bay. Carefully counting tree rings using a hand lens they discovered that the oldest tree had 397 growth rings.  These slow-growing trees can be more than 300 years of age and have a trunk diameter the size of a 50-cent coin.  The world's oldest red cedar is located on the bluff north of Greenleaf in Brown County.  It is approximately 1,290 years-old and happens to be the only known tree more than 1,000 years of age in Wisconsin.   A 507-year-old white cedar is located on Sven's Bluff at Peninsula State Park and another ancient specimen that is 616 years of age can be found at Fish Creek south of the park. 

It is noteworthy that the peninsula happens to be home to this old stuff.  It sort of makes our short human lifetime here on this earth seem all the more inconsequential and small.  

The Green Bay shoreline is characterized by pebble beaches and the cliffs of the escarpment - sometimes call The Ledge.  Moving east the landmass slopes gently to sea level on the Lake Michigan shoreline which is blessed with sand beaches.  Cursed by shallow soils, for most of the county the depth to bedrock is less than five feet.  17% of the landmass has less than 18 to 36 inches of soil with 22% less than 18 inches.  If you live on the escarpment or the northern two-thirds of the peninsula you build your house atop the dolostone bedrock.

Evidence of the most recent glaciation survives.  Eskers can be found in the southwest corner of the county and drumlins and moraines further up the peninsula.  

The highest point in the county can be seen from my house - Brussels Hill towers a mighty 102 feet above the surrounding countryside.

Door County is also home to the state's tallest sand dune.  Located at Whitefish Bay State Park, Old Baldy is 93 feet above the lake level.

That should give you a decent start on the lay of the land around these parts.  Economics, people,  culture and more to follow.

Stay-tuned as I'll be dribbling-out  more Door County factoids from time-to-time.....