3 large bison grazing in green grass, with a baby bison in the background.
American Bison grazing at Tallgrass Prairie Preserve. © Morgan Heim

Places We Protect

Joseph H. Williams Tallgrass Prairie Preserve


The Tallgrass Prairie Preserve is the largest protected remnant of tallgrass prairie left on earth!

The Joseph H. Williams Tallgrass Prairie Preserve is the largest (39,650 acres) protected remnant of tallgrass prairie left on earth. Due to urban sprawl and conversion to cropland, this ecoregion, originally spanning across 14 states from Texas to Minnesota, have left less than 4% remaining of this magnificent landscape 

Since 1989, The Nature Conservancy in Oklahoma has proven successful at restoring this fully-functioning portion of the tallgrass prairie ecosystem with the use of 2,500 free-ranging bison and a "patch-burn" model approach to prescribed burning.


Biodiversity threats in the area include habitat fragmentation and loss, current grazing and fire practices, invasive plant species such as sericea lespedeza and eastern red cedar, and stream degradation due to land management practices and soil erosion.

Conservation In Action

Our "Patch Burn" approach utilizes prescribed burning on roughly 1/3rd of productive rangeland each year, leaving the remaining portions undisturbed by fire. Early research by Oklahoma State University indicates that the complex and mosaic plant communities produced by this "patchy" approach offers huge rewards for biodiversity. Approximately three dozen prescribed burns are conducted each year totaling 15,000 - 20,000 acres. Since 1991, over 730 prescribed burns have been conducted totaling 354,000 acres. In addition we have assisted neighboring ranches burn 518,000 acres and helped them suppress 127 wildfires.

In addition to using prescribed burns on our preserve, we offer offer conservation-minded ranchers an alternative to traditional grazing practices. Conservancy staff have conducted several "patch-burn" workshops with local cattle ranchers to illustrate the potential rewards of embracing this wildlife-friendly method of land management, while continuing to meet the bottom line for their cattle production operations. Beyond alternative grazing practices, we offer to hold conservation easements for land owners who would like to ensure the preservation of their property.

Research On the Ground

Dozens of research initiatives are active on the preserve and over 180 publications in scientific journals have been published with findings from the preserve. The Tallgrass Prairie Ecological Research Station was completed in 2004. This state-of-the-art facility offers field researchers the opportunity to conduct extended studies and initiate laboratory analysis for rangeland research. The research station is also utilized as a workshop destination for university students, researchers and conservation professionals from across the United States.


Please observe the following guidelines when visiting:

  • Bison are dangerous! When viewing bison, there are three rules: #1: Stay in your car. #2: Stay in your car. And #3: Stay in your car 
  • Stay on the trail. Don't collect plants, insects or other species or disturb soil, rocks, artifacts or scientific research markers.
  • No dogs. Preserves harbor ground-nesting birds and other wildlife that are extremely sensitive to disturbance.
  • No bicycles or motorized vehicles. Native plants and research sites are easily trampled.
  • No hunting, camping or campfires.
  • For groups of 10 or more, please contact us before visiting a preserve.
  • Please do not leave behind trash. Bring a bag and carry it out.
  • Please report to us any problems you observe (e.g., camping, plant removal, hunting, off-road vehicle damage, etc).


Tallgrass Prairie Preserve offers some excellent wildlife watching opportunities due to the variety of natural habitats. In addition to the more than 700 plant species on the preserve, more than 300 bird and 80 mammal species make the prairie their home. Visitors can experience the open prairie while viewing bison along the 10-mile driving loop. There are also patches of crosstimbers (upland native oak woodlands) along the route. Designated hiking trails take visitors through bottomland forest, crosstimbers, and prairie. Download a trail guide.

The Prairie in Every Season


  • By mid-May, 600-700 bison calves are frolicking the prairie.
  • Mid‑May through mid‑June, wildflowers cover the fields with blankets of color. Though wildflowers bloom throughout the warm months, they peak in spring, with another fine showing late summer.
  • Prairie chickens boom at sunrise from late March through early May.
  • During the warm months, migrating neotropical species, such as the Dickcissel and Scissor‑tailed flycatcher, are seen frequently.
  • Signature grasses such as big bluestem and switchgrass appear in April, begin producing seed in late July, and continue to, grow through September.


  • By September the big bluestem and switchgrass reach heights of 6 to 8 feet with a few patches stretching to 10 feet. When trees turn to their rich autumn colors, so do the grasses
  • Rough‑legged and Red‑tailed Hawks, Northern Harriers, and Bald and Golden Eagles are common sights during the fall and winter. You also may see deer, coyotes, or bobcats roaming the prairie.


The preserve is open every day from dawn to dusk with no charge for admittance and can be accessed via county roads. There are scenic turnouts, hiking trails, picnic tables, visitor center with gift shop, and public restrooms. The gift shop / visitor center is open from March 1 through December 15 from 10:00am to 4:00pm. It is operated by docents and is typically open every day. Check to see whether the visitor center is open during your visit.

Hunting, fishing, camping, dogs, and off-roading are not allowed on the preserve. 

The Americans With Disabilities Act (ADA) regulations address the use of wheelchairs and “Other Power Driven Mobility Devices” (“OPDMDs) by persons with mobility disabilities. These rules apply to “public accommodations” which include TNC properties that are open to the public. The regulations provide that with regard to “public accommodations” persons with mobility disabilities are entitled to:

  1. Use wheelchairs and manually powered mobility aids (canes, walkers, etc) in areas that are open to pedestrian use.  A “Wheelchair” includes a manually operated device or power-driven device designed primarily for use by an individual with a mobility disability for the main purpose of indoor or both indoor or outdoor locomotion. 
  2. Use OPDMDs if the landowner can make “reasonable modifications to its practices to accommodate them.” An assessment has been done for the Joseph H. Williams Tallgrass Prairie Preserve in accordance with the ADA regulations.



Learn more about our work in Oklahoma and explore the other places we protect.