Native Americans fished, hunted, and camped along the Owyhee River in Leslie Gulch 5,000 years before Europeans came to the area. in 1882, a cattle rancher, Hiram E. Leslie, when working in what was then known as Dugout Gulch, was struck by lightning; thus, the area was renamed Leslie Gulch. The original Leslie Gulch canyon road long served as a wagon and mail route between Rockville and Watson. Today, the town of Watson lies at the bottom of the Owyhee Reservoir.

The most striking features of Leslie Gulch are the diverse and often stark, towering and colorful geologic formations. The Leslie Gulch Tuff (consolidated volcanic ash), which makes up the bulk of these formations, is a rhyolite ash that erupted from the Mahogany Mountain caldera in a series of violent explosions about 15.5 million years ago.

In 1965, seventeen California bighorn sheep were reintroduced into Leslie Gulch. The herd has expanded to over 200 animals. Mule deer and Rocky Mountain elk are also found in the area. Bird watchers can spot Chukar, numerous song birds, raptors, California quail, northern flickers, and white-throated swifts. Coyotes, bobcats, bats and many reptiles, including rattlesnakes, also live in Leslie Gulch