Silver Mound Archaeological Site
One of the most famous archaeological sites in the Midwest is the
Silver Mound quarry/workshop complex in Jackson County, Wisconsin.
Although its name implies that it is a burial mound which contains
precious metal, Silver Mound is neither. The mound is actually a large
sandstone hill that contains layers of cemented silica, forming very hard, brittle rock. This rock,
called "Hixton Silicified Sandstone," "Hixton
Orthoquartzite," or "Sugar Quartz" was a very unique
material used by Native Americans to chip stone tools.
|Bedrock outcropping found at Silver Mound.
The layers of bonded silica which form Hixton Orthoquartzite
distinguish this rock from other sandstone. This rare process of
cementing created material harder than flint. This stronger material
holds sharp edges longer when used as tools such as knives and hide
less re-sharpening. Although several other orthoquartzite quarry sites
have been located in western Wisconsin in recent years, Silver Mound was
the largest and most intensely used source of orthoquartzite in the
Spear-tips made from this Hixton Orthoquartzite have been found as
far away as Mammoth Cave in Kentucky. Some of these points have been
dated at nearly 12,000 years old, revealing that Silver Mound was one of
the first places humans visited in Wisconsin.
Although this site has been investigated since the 1850's, few
details are known about the original activities which took place here.
Over the past century, the mound and its surrounding area have
experienced some disturbances including futile small scale mining for
silver, agricultural plowing, logging and erosion resulting from these
activities. Fortunately, much of the mound remains relatively unaffected
by modern activities, and evidence of past utilization is abundant,
making this one of the best examples of pre-European quarrying and
knapping in North America. Because of its importance and preserved
condition, the site has been listed on the National Register of Historic
Places, and efforts for continued preservation are ongoing.
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The first people known to
occupy or visit the Silver Mound area were bands of nomadic people that
archaeologists call Paleo ("oldest")
Indians. When they
arrived 12,000-9500 years ago, much of northern and eastern Wisconsin
had only recently been covered by glaciers. The land surrounding Silver
Mound was south and west of the glacier's path, and while quite cold,
was lush with vegetation, providing ideal habitat for now-extinct
animals such as the mammoth and mastodon -- woolly elephants which were
larger than their modern counterparts.
These large animals (called megafauna) provided many of the materials
needed by the Paleo Indians to survive in such a harsh climate. Meat was
used for food, bones were used to make tools and perhaps even houses,
and fur was used for clothing to protect themselves from the cold
weather. Since animals were probably their main food source, the Paleo
Indians traveled extensively, either trailing herds or on the lookout
for new ones.
|Projectile points made from Hixton Orthoquartzite.
Roaming the landscape, the Paleo, Indians soon came across Silver
Mound, and here found a wonderful source of stone for making tools. A
wide variety of tools were made, although most of them were used for
hunting, butchering, or processing animal hides. The primary weapon used
for hunting were projectile points, ( hafted onto spear shafts. Stone knives cut the fur
or meat, and hide scrapers were used to deflesh and dehair the animal skins.
Scrapers (top) and knives (bottom) made from Hixton Orthoquartzite.
How do we know people were at Silver Mound 12,000 years ago?
Distinctive "fluted" points have been found embedded in
mammoth and mastodon skeletons in other parts of the country, and Carbon
14 testing done on the bones dated them to 11,000-12,000 years before
present. No confirmed kill sites have yet been found in Wisconsin, but
found here are the same as those carbon dated in others areas. The
similarity of point styles implies that the Wisconsin points are also
that old, and that people inhabited the area at that time.
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Late Prehistoric People
After the glaciers melted, the people who lived in Wisconsin had to
adapt to changing climatic conditions and animal habitats. Mastodons,
mammoths and other megafauna became extinct by about 10,000 years ago.
At the same time, the climate became warm and dry, creating a
prairie-like habitat perfect for bison. Numerous bison bones have been found in nearby Buffalo and Trempealeau
counties. This particular species, Bison Occidentalis, is now extinct,
but was known to have lived in the United States until 8,000 years ago.
Throughout this period hunting continued to be a prime activity, and the
bison hunters continued to return to Silver Mound to use Hixton
Silicified Sandstone to replenish their stone tools.
|Throwing a spear with an atlatl.
(drawing courtesy of
During the Archaic culture (9500-3500 years ago), Silver Mound was
surrounded by a prairie/savanna. This prairie would have been an ideal
habitation for bison, elk and deer. During this period Archaic hunters
continued using spears and spear throwers, called atlatls. The atlatl provided the hunter more power and distance. The end
of the Archaic culture coincides with a shift to a moister environment,
and increased forest. By about 5,000 years ago bison herds were probably
gone from Wisconsin. Instead, the people focused on hunting deer and elk
and harvesting fish and other floodplain resources.
|Projectile points from the Archaic, Woodland and Oneota
Woodland and Oneota Cultures
The last two prehistoric groups to reside in Wisconsin were the
Woodland (1000-1500 years ago) and Oneota (500-1000 years ago) cultures.
The climate during these two periods was very similar to that of the
present. Silver Mound was on the edge of two environmental areas, with prairie and deciduous forest to the southwest and conifer/hardwood
forests to the northeast. The mixture of pine forests, oak savannas and
conifer swamps was the perfect setting for animals such as deer, elk,
black bear, and others which are still living in Wisconsin today, and a variety of plants such as nuts and berries.
Hunting continued to be the prime source of food for these cultures,
although corn agriculture was introduced about 1000 years ago. Also, the
introduction of the bow and arrow around 1200 years
ago generally replaced the atlatl. Still the people returned to Silver
Mound for stone tools supplies.
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The first Euro-Americans in Jackson County were aware that this area
had been utilized. Walking through the woods, they noticed quarry pits,
which the Native Americans had dug hundreds and
thousands of years earlier to obtain Hixton Silicified Sandstone. The
first Europeans assumed the extensive pits meant valuable metals must
|Prehistoric quarry pits
(depressions in ground) at Silver Mound.
One account suggests that the first European searching for metal at
Silver Mound was the French explorer Pierre LeSuer, whose presence is
documented on the Mississippi River as early as the year 1700. The first
European settlers in Jackson County arrived in the 1840's, and soon came
to accept the legend of a "lost silver mine" in the area. This
legend suggests that a party of miners arrived in 1855 equipped with a
beaver pelt map, which they had received from a Frenchman in St. Louis,
leading them to Silver Mound. They found no silver, and by 1860 the idea
of silver being found there was discredited by geologists, although
further mining was attempted by prospectors in 1871-1873 and 1895.
20th Century Occupants
Over the years, Silver Mound has been used for many purposes
including a campground for the past several decades. Other sections of
Silver Mound and surrounding areas have been used as homesteads and
farmland since the 1840's. The area which was once a marshy habitat for
mammoths and mastodons has become fields used for growing crops such as
corn and alfalfa.
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Archaeological Testing at Silver Mound
Brown’s sketch map
of archaeological features at Silver Mound in the early 1930's (taken
from The Wisconsin Archeologist Volume 65, Number 2, June 1984).
The many activities which have occurred at Silver Mound over the past
12,000 years have changed the mound's appearance. The quarrying efforts
of the Native Americans, and the mining and agricultural efforts of
Euro-Americans has caused erosion to occur in several places. Several ravines, including the one opening up to KOA campground, have been
expanded by these activities, resulting in soil washing to lower areas
surrounding Silver Mound. Artifacts from any of the cultures mentioned
above could be buried at Silver Mound by this soil.
The first professional archaeologist to examine Silver Mound was Will
C. McKern of the Milwaukee Public Museum in 1928. Charles E. Brown, of
the State Historical Society of Wisconsin, created the first detailed
records (notes and maps) of parts of the mound in 1932 and 1933. Since
the 1960's several excavations have been conducted at specific areas
within Silver Mound, by various universities, confirming the use of
Silver Mound by prehistoric people.
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Special Features on Silver Mound
Dwyer Rockshelter rockshelter has long been the focus of interest at
Silver Mound. An 1860 geological account of Silver Mound mentions this
cave and a smaller one nearby which contained many glyphs. When visited
by archaeologist Charles E. Brown in 1932 and 1933, the name of owner
"Harry Dwyer 1919" was carved into the top of the front of
this shelter, where it remains today. Unfortunately, the glyphs noted in
the 1860's are no longer visible.
Although the shelter was undoubtedly dug into many times since 1850,
the first archaeologist to dig here was Harris Palmer of Platteville,
who found flakes and pottery fragments. More intensive excavations were
undertaken by UW-Oshkosh and UW-Milwaukee in the 1970's and carbon 14
dates as early as 9500 years ago were obtained from charcoal found
beneath a rock on the floor of the shelter. This shelter is now
interpreted as a seasonal campsite by peoples coming to Silver Mound to
replenish their stone tool kits, and was undoubtedly used as such for
thousands of years.
There are at least two remaining rock art sites at Silver Mound,
including a small overhang near the Dweyer Rockshelter contains four
red-painted figures on the roof of the rockshelter. On the ceiling of
this rock outcrop is a series of faint red paintings. One image is a
bird-like figure composed of five vertical bars curving downward from a horizontal bar . Other
figures appear to represent partially eroded quadrupeds such as buffalo.
The legs and bellies are relatively clear, though the heads and backs
are largely gone.
Prehistoric quarrying is still evident on Silver Mound. The slopes of
the mound show hundreds of depressions that are quarry pits. The pits
range from less than 3 feet to over 10 feet in depth, and up to 30 feet
in diameter. Proof that these depressions were at one time quarrying
pits is exhibited by flakes found in rodent spoil piles, logging scars
and roots of fallen trees.
Survey of the quarry pits in 1932 by Charles E. Brown led to the
discovery of several "rounded quartzite hammers" which weighed
between five and ten pounds. Brown felt the hammers had been used by
prehistoric people to break up the rock, as there were large layers of
Hixton Orthoquartzite lying outside the pits.
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Future of Silver Mound
In addition to the use of Silver Mound for
camping and agricultural purposes, portions of the mound have been
purchased by the Archaeological Conservancy whose
mission is to preserve archaeological sites throughout the United
States. Their objective in purchasing this land was to ensure that
future use on Silver Mound will not damage its cultural resources.
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The following are a few resources that will help you learn more about
- Comments on Brown's Research at Silver Mound. Jeffrey A. Behm. The
Wisconsin Archaeologist. Volume 65, Number 2, June 1984.
- Introduction: Wisconsin Archaeology. William Green, James B.
Stoltman & Alice B. Kehoe, ed. The Wisconsin Archaeologist.
Volume 67, Number 3-4,
- Wisconsin Archaeology (edited by Robert Birmingham, Carol I. Mason,
and James Stoltman). The Wisconsin Archeologist 78(1-2). 1997.
- Notes on Silver Mound. Charles E. Brown. The Wisconsin Archaeologist.
Volume 65, Number 2, June 1984.
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