A man sits in a wooden boat with a mast on the edge of the Colorado River in the Black Canyon, Mojave County, Arizona. At this time, photographer Timothy O'Sullivan was working as a military photographer, for Lt. George Montague Wheeler's U.S. Geographical Surveys West of the One Hundredth Meridian. Photo taken in 1871, from expedition camp 8, looking upstream. #

Panoramic view of tents and a camp identified as "Camp Beauty", rock towers and canyon walls in Canyon de Chelly National Monument, Arizona. Tents and possibly a lean-to shelter stand on the canyon floor, near trees and talus. Photographed in 1873. #

Boat crew of the "Picture" at Diamond Creek. Photo shows photographer Timothy O'Sullivan, fourth from left, with fellow members of the Wheeler survey and Native Americans, following ascent of the Colorado River through the Black Canyon in 1871 #

Timothy O'Sullivan's darkroom wagon, pulled by four mules, entered the frame at the right side of the photograph, reached the center of the image, and turned around, heading back out of the frame. Footprints lead from the wagon toward the camera, revealing the photographer's path. Photo taken in 1867, in the Carson Sink, part of Nevada's Carson Desert. #

A wooden balanced incline used for gold mining, at the Illinois Mine in the Pahranagat Mining District, Nevada in 1871. An ore car would ride on parallel tracks connected to a pulley wheel at the top of tracks. #

In 1867, O'Sullivan traveled to Virginia City, Nevada to document the activities at the Savage and the Gould and Curry mines on the Comstock Lode, the richest silver deposit in America. Working nine hundred feet underground, lit by an improvised flash—a burning magnesium wire, O'Sullivan photographed the miners in tunnels, shafts, and lifts. #

Nearly 150 years ago, photographer O'Sullivan came across this evidence of a visitor to the West that preceded his own expedition by another 150 years—A Spanish inscription from 1726. This close-up view of the inscription carved in the sandstone at Inscription Rock (El Morro National Monument), New Mexico reads, in English: "By this place passed Ensign Don Joseph de Payba Basconzelos, in the year in which he held the Council of the Kingdom at his expense, on the 18th of February, in the year 1726". #

View of the White House, Ancestral Pueblo Native American (Anasazi) ruins in Canyon de Chelly, Arizona, in 1873. The cliff dwellings were built by the Anasazi more than 500 years earlier. At bottom, men stand and pose on cliff dwellings in a niche and on ruins on the canyon floor. Climbing ropes connect the groups of men. #

The south side of Inscription Rock (now El Morro National Monument), in New Mexico in 1873. Note the small figure of a man standing at bottom center. The prominent feature stands near a small pool of water, and has been a resting place for travelers for centuries. Since at least the 17th century, natives, Europeans, and later American pioneers carved names and messages into the rock face as they paused. In 1906, a law was passed, prohibiting further carving. #