Over the past century, roughly 90% of Arizona's free-flowing year-round rivers and streams have disappeared due to human use of desert waters. These rivers and streams once supported riparian areas that provided water, food, and protection to myriad plants, animals, and even humans. You can get an idea of what such riparian areas were like by visiting this sprawling preserve, which is located 8 miles east of Sierra Vista. Fossil findings from this area indicate that people were living along this river as much as 13,000 years ago. At that time, this area was a swamp, not a desert. Today, the San Pedro River is all that remains of this ancient wetland, and, due to an earthquake a century ago, much of the San Pedro's water now flows underground. Don't expect a wide, rushing river when you visit the San Pedro; what you'll see here would be called a creek anywhere but Arizona. Still, the water attracts wildlife, especially birds, and the conservation area is very popular with birders, who have a chance of spotting more than 350 species here.

Also within the riparian area is the Murray Springs Clovis Site, where 16 spear points and the remains of a 13,000-year-old mammoth kill were found in the 1960s. Although there isn't much to see other than some trenches, there are numerous interpretive signs along the short trail through the site. It's just north of Ariz. 90 about 5 miles east of Sierra Vista.

For a glimpse of the region's Spanish history, visit the ruins of the Presidio Santa Cruz de Terrenate, about 20 miles northeast of Sierra Vista off Ariz. 82 near the ghost town of Fairbank. This military outpost was established in 1775 or 1776 but was never completed due to the constant attacks by Apaches. Today only decaying adobe walls remain. To reach this site, take Ariz. 82 east from U.S. 90 and drive north 1 3/4 miles on Ironhorse Ranch Road, which is at milepost 60. It's a 1.3-mile hike to the site.

To visit Fairbank ghost town, drive Ariz. 82 to the bridge over the San Pedro River. Here you'll find the remains of several buildings from the heyday of this former railroad town. Fairbank, which was founded in the 1880s to serve nearby silver-mining towns, once had a population of nearly 15,000 people. Today, only one of the old buildings has been restored and opened to the public. The old Fairbank School is now the Fairbank Schoolhouse Museum and Store (tel. 520/457-3062) and is open Friday through Sunday from 9:30am to 4:30pm; admission is free. From Fairbank, several miles of hiking trails lead along the San Pedro River. You can walk to two other ghost towns, Millville and Charleston, but there is very little to see at either of these old town sites. It is also possible to walk from Fairbank to the ruins of the Presidio Santa Cruz de Terrenate.

For bird-watching, the best place is the system of trails at the Ariz. 90 crossing of the San Pedro. Here you'll find the San Pedro House, a 1930s ranch that is operated as a visitor center and bookstore. It's open daily from 9:30am to 4:30pm and has information on guided walks and hikes, bird walks, bird-banding sessions, and other events that are scheduled throughout the year. Outside the old ranch house, there's a huge old cottonwood tree.