"Our country calls not for the life of ease but for the life of strenuous endeavor," Theodore Roosevelt famously said in an 1899 speech.

Inspired by Roosevelt's long-ago declaration, my wife, Nancy, and I headed to the North Dakota Badlands to explore the landscape that had such an impact on the president's life and where he himself had practiced what he preached.

Teddy Roosevelt first visited the rugged landscape in 1883. The next year, he returned to the wide open spaces he adored after the deaths of his wife and mother, on the same night, in the same house, in New York. Roosevelt eventually owned an interest in two cattle ranches there.

The semi-arid land of colorful buttes, rugged ravines and plateaus of grasslands — all sculpted for millions of years by water and wind — seems made for adventure. It is a great place to practice Roosevelt's vigorous life. In 1978, the 70,500-acre Theodore Roosevelt National Park was established there.

My wife and I decided to explore the large southern unit of the three-unit park. Our 10-hour drive on Interstate 94 was rewarded with the appearance of the Little Missouri Badlands, a place Roosevelt described as one of "grim beauty." Dakota Indians called this mako shika or the "no good land." A frontier soldier described it as "hell with the fire put out."

Summers can be hot in the badlands, and vegetation has adapted to temperature swings. Prickly pear cactuses, yucca and some of the short prairie grasses such as grama grass and little bluestem thrive here. But the park is most inviting in the fall, when the riparian cottonwoods, sunflowers and rabbitbrush are yellowing and the small blue asters match the common appearance of dry blue skies.

The cool nights inspire coyote song, passing migratory waterfowl and good sleep for the camper.

We stopped at the park's visitor center to pick up maps, wander through the historical and natural history exhibits and watch the excellent short introductory film. Then we headed north in our car, parked at a trailhead, and hiked on a path that would take us to the Petrified Forest. We hiked a couple of miles, giving a wide berth to a handsome big bison bull that lolled, almost like a sentry, on the trail. As many as 800 bison (600 in the southern unit) roam freely in the park.

It seems incongruous that this arid region was once a tropical forest, where tall trees cast shade. The large petrified stumps, some 4 and 5 feet across, look out of place in a land that now runs on the dry side.

On the bison trail

The following day we biked the lovely and paved 25-plus-mile loop that gives a good sampling of what the park is about. The smooth curves and roller-coaster hills worked our hearts and then exhilarated us on the lovely downhill runs. Along the way, we parked our bikes at various trailheads, giving our cycling muscles a break, to walk a ways or inspect prairie dog towns or bison herds.

Next, it was time to hike. While the park has miles of established and marked trails, we wanted to go off-trail. When we shared our plans with park rangers at the visitor center, they strongly suggested that we carry plenty of water, some food and use great caution when crossing the Little Missouri River.

"Look for bison crossing points," a young woman instructed us. With the wetter summer, the turbid Little Missouri was higher than typical in autumn, so she suggested that we ford the river where the bison cross. Bison, she said, don't like to swim so they know where they can wade the river.

The next day we packed four water bottles, food, binoculars and a camera and walked away from our campsite. We forded the knee-deep river and soon learned that bison aren't much different from humans when choosing paths. They look for the easiest route. Consequently, much of our free-ranging hike was spent moving from bison trail to bison trail. At high vantage points, we chose our next route, giving a wide berth to those docile-looking beasts.

The day before we roamed, a tourist had stepped away from his car to get closer to placid-looking bison that were grazing nearby. A nearby bison suddenly lunged at the man. This was no bluff charge; the man was hit. Emergency responders were soon on the scene and the injured man taken away.

Rolling over a trail

We also inquired about mountain biking. While backcountry mountain biking is not allowed and there are no mountain bike trails in the park, rangers gave us a map of the nearby Maah Daah Hey trail. The Mandan Hidasta name means "Grandfather."

This 96-mile trail has been in use for centuries, first as a trade route for early American Indians and later for early European travelers. Today it provides a spectacular stretch of single-track trail that passes Roosevelt's Elkhorn Ranch site on the Little Missouri River. Hikers and horseback riders also use the trail.

Again, packing plenty of water and food is encouraged. And don't forget the sunscreen.

After our fourth night, we headed back home to Minnesota for a deserved rest from the strenuous life. Teddy would have given us a hearty, "Bully for you!!"

Tom Anderson, of North Branch, Minn., is the author of "Things That Bite: The Truth About Critters That Scare People."