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Wisconsin State Natural Areas Program Observatory Hill (No. 223)

Observatory Hill

Photo by Thomas A. Meyer



Marquette County. T14N-R10E, Section 8. 208 acres.



The highest point in Marquette County is Observatory Hill, an isolated outcropping of porphyritic rhyolite rising 300 feet above the surrounding landscape. The fine-grained rhyolite, an igneous rock embedded with feldspar crystals, is highly resistant to erosion and has been dated to 1.76 billion years ago. On the exposed rocks at the summit are polished rock surfaces with grooves, striations, and chatter marks created by the passage of the glacial Cary icesheet 12,000 years ago. Recently, scientists have discovered the existence of petroglyphs on the hill’s rock outcroppings, which may be part of a larger prehistoric petroform found in Marquette County. The slopes are covered with a southern dry forest community dominated by red and white oak, basswood and shagbark hickory and much of the area is now being restored to oak savanna – an imperiled vegetation community in Wisconsin. Near the top of the hill, bedrock is exposed or close to the surface creating acidic conditions where a specialized glade community has developed. Red cedar dominates the glade and the thin soils support a sparse ground cover of mosses, ferns, and lichens. The hill has long been known by naturalists and was a favorite childhood haunt of John Muir who lived nearby. Observatory Hill is owned by the DNR and was designated a State Natural Area in 1989.

Note: There is a planned timber harvest being conducted as part of a long-term oak savanna restoration. See the flyer for more information.


Driving directions

From the intersection of Highways 22 and F on the south side of Montello, go south on F 4.8 miles, then east on 14th Road 0.5 mile, then south on 13th Road 1.4 miles, then east on Gillette Avenue 0.6 mile to a parking area north of the road. A footpath to the summit begins at the northwest corner of the old field.


Observatory Hill is owned by:

  • WDNR
  • Private


The DNR's state natural areas program is comprised of lands owned by the state, private conservation organizations, municipalities, other governmental agencies, educational institutions and private individuals. While the majority of SNAs are open to the public, access may vary according to individual ownership policies. Public use restrictions may apply due to public safety, or to protect endangered or threatened species or unique natural features. Lands may be temporarily closed due to specific management activities. Users are encouraged to contact the landowner for more specific details.

The data shown on these maps have been obtained from various sources, and are of varying age, reliability, and resolution. The data may contain errors or omissions and should not be interpreted as a legal representation of legal ownership boundaries.


Site objectives

Manage the site as an oak opening and cedar glade reserve, as a significant geological site, and as an ecological reference area. Natural processes will determine the structure of the site's natural communities, along with prescribed vegetation manipulation in the savanna (see below). Provide opportunities for research and education on the highest quality native oak openings and cedar glades.

Management approach

The site is not currently functioning as an ecological reference area and needs to be restored to that function. The native cedar glade species are mostly managed passively, allowing nature to determine their ecological characteristics. However, some thinning of the red cedars, invasives control, or fire may be needed to mimic natural disturbance patterns. The native dominant savanna tree species (primarily oaks) will be actively managed to convert the forest to oak woodland and oak opening. Understory manipulation and shrub control via harvest, brushing or fire may be needed to mimic natural disturbance patterns. Augmentation of the ground layer will only add species that historically would have been found on the site, utilizing seeds or plugs from local genetic material; this usually occurs in the early stages of restoration. Other allowable activities across the entire site include control of invasive plants and animals, maintenance of existing facilities, and access to suppress wildfires. In the savanna, salvage of trees after a major wind event can occur if the volume of woody material inhibits fire prescriptions.

Site-specific considerations

  • Roadside easement area may be managed sporadically by township.
  • The pine plantation will be thinned and harvested, and conversion to oak opening will be promoted.
  • Southern dry forest and oak opening species will be allowed to invade the old field, which may be augmented with planting of locally-collected ground layer species.


Management objectives and prescriptions


Very few State Natural Areas have public facilities, but nearly all are open for a variety of recreational activities as indicated below. Generally, there are no picnic areas, restrooms, or other developments. Parking lots or designated parking areas are noted on individual SNA pages and maps. Trails, if present, are typically undesignated footpaths. If a developed trail is present, it will normally be noted on the SNA map and/or under the "Access" tab. A compass and topographic map or a GPS unit are useful tools for exploring larger, isolated SNAs.

Hunting and trapping

This SNA has multiple landowners: Opportunities for hunting and trapping depend on the land owner. In general, most DNR-owned land allows hunting and trapping. Partner-owned land may have other rules (for example, university-owned lands do not allow hunting or trapping). Please contact them directly to find out about their rules for hunting and trapping. You can find a link to other owner websites under the "Resource links" heading above. More details regarding allowable uses on the non-DNR land may be found under the "Access" tab above, if available.

Allowable activities: DNR-owned land

In general, the activities listed below are allowed on all DNR-owned SNA lands. Exceptions to this list of public uses, such as SNAs closed to hunting, are noted under the "Access" tab above and posted with signs on site.

  • Hiking
  • Fishing
  • Cross country skiing
  • Hunting
  • Trapping

Prohibited activities: all SNAs

  • Camping and campfires
  • Collecting of animals (other than legally harvested species), non-edible fungi, rocks, minerals, fossils, archaeological artifacts, soil, downed wood, or any other natural material, alive or dead. Collecting for scientific research requires a permit issued by the DNR
  • Collecting of plants including seeds, roots or other non-edible parts of herbaceous plants such as wildflowers or grasses
  • Geocaching
  • Horseback riding
  • Rock climbing
  • Vehicles, including bicycles, ATVs, aircraft, and snowmobiles except on trails and roadways designated for their use

For rules governing state-owned SNAs and other state lands, please consult Chapter NR 45 Wis. Admin. Code [exit DNR]

Last revised: Friday, October 26, 2018