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. Originally spanning portions of 14 states from Texas to Minnesota, urban sprawl and conversion to cropland have left less than 4% of this magnificent American landscape. Since 1989, the Conservancy has proven successful at restoring this fully-functioning portion of the tallgrass prairie ecosystem with the use of about 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. One way to measure the success of efforts to restore biodiversity is to track species.

What the Conservancy is doing now will offer conservation-minded ranchers an alternative to traditional grazing practices. Conservancy staff have already conducted several "patch-burn" workshops with area 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. In addition to alternative grazing practices, The Nature Conservancy is offering to hold conservation easements for land owners who would like to ensure the preservation of their property.

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.

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 will also be utilized as a workshop destination for university students, researchers and conservation professionals from across the United States.

More than three dozen research projects are active on the preserve, and 180 publications in scientific journals have been produced. An exciting "patch-burn" was initiated with Oklahoma State University in 2001 on 11,000 acres. The objective is to develop and export creative cattle management techniques that will improve wildlife habitat diversity, while maintaining a profit margin for cattle ranchers.  


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. Click here to download a trail guide ►

The prairie puts on a different show for every season and each has its own unique beauty:


  • 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. Click here to see if the visitor center is open during your visit

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

More About Bison

A Historical Perspective
Great herds of bison once roamed North America between the Appalachian Mountains and the Rocky Mountains.

Origin of the Tallgrass Herd
The Tallgrass Prairie bison herd was started with 300 animals donated by the Ken-Ada Ranch.

Tallgrass Bison Herd Size
The original herd of 300 bison at Tallgrass Prairie Preserve has grown to the optimum over-wintered size of about 2,100, which is based on the available range.

Bison Vital Statistics
Bison can weigh as much as 2000 pounds, stand over six feet tall and live as long a 40 years.

Bison Behavior
Bison are grazers who prefer grasses to other prairie plants, such as wildflowers.

Bison Personality
Bison are ordinarily mild-mannered, even dull, animals but can be aggressive.

Bison License Plate

Show your Okie pride and support conservation with a special-interest bison license plate. Order yours today!

Watch this Majestic Video of Bison Roundup

Enjoy the sights and sounds of these iconic beasts in this magical video filmed at the Tallgrass Prairie Preserve during the annual bison roundup.

Confronting a Deadly Disease

Confronting the spread of M. bovis among the bison at Tallgrass Prairie Preserve may save herds across the country.

Bouncing Baby Bison!

Melt your heart with this collection of our bundles of joy at Tallgrass Prairie Preserve. This overload of cuteness is certain to make your day!