Hiking and mountain biking on trails are healthy and inexpensive outdoor activities. Idaho is graced with numerous high-profile trails that are part of the National Trails System.

Scenic Trails are protected corridors with outstanding recreational opportunities.

Historic Trails honor well-known routes used in past years by explorers, immigrants, traders or the military. Rich in history, they're made up of segments of original trails and historic sites. Often, they link with auto tour routes.

The national trails system was established in 1968 with the passing of the National Trails System Act. There are more than 60,000 miles of trails in the United States. They range from hundreds to thousands of miles long.

The 3,200-mile Continental Divide National Scenic Trail goes from Mexico to Canada. It enters eastern Idaho near Island Park and weaves through portions of Idaho and Montana.

Three of the 17 national historic trails cross through Idaho. The famous 4,400-mile Lewis and Clark National Historic Trail passes through northern Idaho, as does the 1,170-mile Nez Perce National Historic Trail.

Celebrations are now under way in Idaho for the Oregon National Historic Trail.

This 2,170-mile trail winds through southern Idaho and once was a key part of the westward expansion of the United States during the early 1840s. More than 500,000 people followed the trail to California, Utah and the Pacific Northwest.

Historic sites and 300 miles of visible wagon ruts make this trail popular in Idaho.

A wagon train is crossing Idaho as part of the Oregon-California Trails Association (OCTA) annual conference, which is being held in Nampa this year.

"It's a teaching week where people learn more about the historic trails in the West," said Jim McGill of Nampa, who serves as the historical trails preservation officer with the Idaho chapter of the OCTA.

The wagon train departed from the National Oregon-California Trail Center in Montpelier on July 9. After camping at about 24 sites along the trail, wagons, riders and walkers are scheduled to arrive in Nampa on Aug. 4.

Traveling an average of 18 miles per day, the wagon train consists of five wagons that are scheduled to complete the entire route and as many as 20 wagons that will travel on segments of the trail. Two wagons are set up for visitors to ride. Walkers and horseback riders are invited to join for a small fee. The Blacks Creek area and Kuna are places to see or join the wagon train.

In addition, 10 all-day bus tours to various historic destinations start from the Nampa Civic Center on Thursday, Aug. 7 and Saturday, Aug. 9. Sign up and pay in advance. The public is welcome to join for the full conference or attend for a day. Check the OCTA Web site (www.octa-trails.org) for details.

Tours include guides who give bus and on-site lectures. Destination choices include Cambridge, Owyhee County, eastern Oregon, Hagerman and the Boise Valley.

"We plan the tours where they can see the remnants of the trails," said McGill.

One bus tour goes to the annual Oregon Trail wagon crossing at Three Island State Park in Glenns Ferry on Aug. 9. Wagon train drivers reenact the crossing of the Snake River.

If you miss the conference tours and lectures, consider participating in one of the monthly tours offered through the Idaho Chapter of OCTA. Tours head to locations where you can see the original ruts. During some of the outings, participants mark and re-mark portions of the trail.

Consider visiting the National Trails System, where history and scenery abound.

Natalie Bartley is a freelance outdoors writer. Her column runs each Thursday in the Idaho Outdoors magazine. Natalie can be contacted by e-mail: natbartley@earthlink.net