I remember it vividly, and my text messages, hand-scribbled notes and audio recordings keep the memories of our day at Nachusa Grasslands fresh.

As Quad-City Times photographer Andy Abeyta and I approached the 4,000-acre nature preserve, located about 80 miles east of the Quad-Cities near Dixon, Illinois, we kept our eyes peeled for our subject: American bison.

We recorded our first sighting of the grand mammals — North America's largest — from the road, easing our worries we had set ourselves up for a goose chase on the prairie.

Upon arrival, we added layers and traded our shoes for hiking boots. My phone sounded with a text message from Bill Kleiman, Nachusa's project director.

"Door open. B there in a minute. Coffee on."

After gulping down a couple eye-widening cups, we set out on foot, accompanied by the veteran conservationist, into the horned herd's domain.

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In the 19th century, human pressures exterminated bison in the Midwest. In recent years, however, environmental groups in Illinois and Iowa have reintroduced hundreds of the grazing beasts to help rejuvenate grassland ecosystems that once covered large swaths of both states.

Read more about these animals, their journey and the roles they play in prairie restoration, in this week's Big Story in the Sunday edition of the Quad-City Times and online at qctimes.com.